SQLAlchemy 2.0 Documentation
SQLAlchemy Core
- SQL Statements and Expressions API
- Column Elements and Expressions
- Operator Reference
- SELECT and Related Constructs¶
- Selectable Foundational Constructors
- Selectable Modifier Constructors
- Selectable Class Documentation
Alias
AliasedReturnsRows
CompoundSelect
CompoundSelect.add_cte()
CompoundSelect.alias()
CompoundSelect.as_scalar()
CompoundSelect.c
CompoundSelect.corresponding_column()
CompoundSelect.cte()
CompoundSelect.execution_options()
CompoundSelect.exists()
CompoundSelect.exported_columns
CompoundSelect.fetch()
CompoundSelect.get_execution_options()
CompoundSelect.get_label_style()
CompoundSelect.group_by()
CompoundSelect.is_derived_from()
CompoundSelect.label()
CompoundSelect.lateral()
CompoundSelect.limit()
CompoundSelect.offset()
CompoundSelect.options()
CompoundSelect.order_by()
CompoundSelect.replace_selectable()
CompoundSelect.scalar_subquery()
CompoundSelect.select()
CompoundSelect.selected_columns
CompoundSelect.self_group()
CompoundSelect.set_label_style()
CompoundSelect.slice()
CompoundSelect.subquery()
CompoundSelect.with_for_update()
CTE
Executable
Exists
FromClause
FromClause.alias()
FromClause.c
FromClause.columns
FromClause.description
FromClause.entity_namespace
FromClause.exported_columns
FromClause.foreign_keys
FromClause.is_derived_from()
FromClause.join()
FromClause.outerjoin()
FromClause.primary_key
FromClause.schema
FromClause.select()
FromClause.tablesample()
GenerativeSelect
HasCTE
HasPrefixes
HasSuffixes
Join
Lateral
ReturnsRows
ScalarSelect
Select
Select.__init__()
Select.add_columns()
Select.add_cte()
Select.alias()
Select.as_scalar()
Select.c
Select.column()
Select.column_descriptions
Select.columns_clause_froms
Select.correlate()
Select.correlate_except()
Select.corresponding_column()
Select.cte()
Select.distinct()
Select.except_()
Select.except_all()
Select.execution_options()
Select.exists()
Select.exported_columns
Select.fetch()
Select.filter()
Select.filter_by()
Select.from_statement()
Select.froms
Select.get_children()
Select.get_execution_options()
Select.get_final_froms()
Select.get_label_style()
Select.group_by()
Select.having()
Select.inherit_cache
Select.inner_columns
Select.intersect()
Select.intersect_all()
Select.is_derived_from()
Select.join()
Select.join_from()
Select.label()
Select.lateral()
Select.limit()
Select.offset()
Select.options()
Select.order_by()
Select.outerjoin()
Select.outerjoin_from()
Select.prefix_with()
Select.reduce_columns()
Select.replace_selectable()
Select.scalar_subquery()
Select.select()
Select.select_from()
Select.selected_columns
Select.self_group()
Select.set_label_style()
Select.slice()
Select.subquery()
Select.suffix_with()
Select.union()
Select.union_all()
Select.where()
Select.whereclause
Select.with_for_update()
Select.with_hint()
Select.with_only_columns()
Select.with_statement_hint()
Selectable
SelectBase
SelectBase.add_cte()
SelectBase.alias()
SelectBase.as_scalar()
SelectBase.c
SelectBase.corresponding_column()
SelectBase.cte()
SelectBase.exists()
SelectBase.exported_columns
SelectBase.get_label_style()
SelectBase.inherit_cache
SelectBase.is_derived_from()
SelectBase.label()
SelectBase.lateral()
SelectBase.replace_selectable()
SelectBase.scalar_subquery()
SelectBase.select()
SelectBase.selected_columns
SelectBase.set_label_style()
SelectBase.subquery()
Subquery
TableClause
TableClause.alias()
TableClause.c
TableClause.columns
TableClause.compare()
TableClause.compile()
TableClause.corresponding_column()
TableClause.delete()
TableClause.description
TableClause.entity_namespace
TableClause.exported_columns
TableClause.foreign_keys
TableClause.get_children()
TableClause.implicit_returning
TableClause.inherit_cache
TableClause.insert()
TableClause.is_derived_from()
TableClause.join()
TableClause.lateral()
TableClause.outerjoin()
TableClause.params()
TableClause.primary_key
TableClause.replace_selectable()
TableClause.schema
TableClause.select()
TableClause.self_group()
TableClause.table_valued()
TableClause.tablesample()
TableClause.unique_params()
TableClause.update()
TableSample
TableValuedAlias
TextualSelect
TextualSelect.add_cte()
TextualSelect.alias()
TextualSelect.as_scalar()
TextualSelect.c
TextualSelect.compare()
TextualSelect.compile()
TextualSelect.corresponding_column()
TextualSelect.cte()
TextualSelect.execution_options()
TextualSelect.exists()
TextualSelect.exported_columns
TextualSelect.get_children()
TextualSelect.get_execution_options()
TextualSelect.get_label_style()
TextualSelect.inherit_cache
TextualSelect.is_derived_from()
TextualSelect.label()
TextualSelect.lateral()
TextualSelect.options()
TextualSelect.params()
TextualSelect.replace_selectable()
TextualSelect.scalar_subquery()
TextualSelect.select()
TextualSelect.selected_columns
TextualSelect.self_group()
TextualSelect.set_label_style()
TextualSelect.subquery()
TextualSelect.unique_params()
Values
ScalarValues
- Label Style Constants
- Insert, Updates, Deletes
- SQL and Generic Functions
- Custom SQL Constructs and Compilation Extension
- Expression Serializer Extension
- SQL Expression Language Foundational Constructs
- Visitor and Traversal Utilities
- Schema Definition Language
- SQL Datatype Objects
- Engine and Connection Use
- Core API Basics
Project Versions
- Previous: Operator Reference
- Next: Insert, Updates, Deletes
- Up: Home
- On this page:
- SELECT and Related Constructs
- Selectable Foundational Constructors
- Selectable Modifier Constructors
- Selectable Class Documentation
Alias
AliasedReturnsRows
CompoundSelect
CompoundSelect.add_cte()
CompoundSelect.alias()
CompoundSelect.as_scalar()
CompoundSelect.c
CompoundSelect.corresponding_column()
CompoundSelect.cte()
CompoundSelect.execution_options()
CompoundSelect.exists()
CompoundSelect.exported_columns
CompoundSelect.fetch()
CompoundSelect.get_execution_options()
CompoundSelect.get_label_style()
CompoundSelect.group_by()
CompoundSelect.is_derived_from()
CompoundSelect.label()
CompoundSelect.lateral()
CompoundSelect.limit()
CompoundSelect.offset()
CompoundSelect.options()
CompoundSelect.order_by()
CompoundSelect.replace_selectable()
CompoundSelect.scalar_subquery()
CompoundSelect.select()
CompoundSelect.selected_columns
CompoundSelect.self_group()
CompoundSelect.set_label_style()
CompoundSelect.slice()
CompoundSelect.subquery()
CompoundSelect.with_for_update()
CTE
Executable
Exists
FromClause
FromClause.alias()
FromClause.c
FromClause.columns
FromClause.description
FromClause.entity_namespace
FromClause.exported_columns
FromClause.foreign_keys
FromClause.is_derived_from()
FromClause.join()
FromClause.outerjoin()
FromClause.primary_key
FromClause.schema
FromClause.select()
FromClause.tablesample()
GenerativeSelect
HasCTE
HasPrefixes
HasSuffixes
Join
Lateral
ReturnsRows
ScalarSelect
Select
Select.__init__()
Select.add_columns()
Select.add_cte()
Select.alias()
Select.as_scalar()
Select.c
Select.column()
Select.column_descriptions
Select.columns_clause_froms
Select.correlate()
Select.correlate_except()
Select.corresponding_column()
Select.cte()
Select.distinct()
Select.except_()
Select.except_all()
Select.execution_options()
Select.exists()
Select.exported_columns
Select.fetch()
Select.filter()
Select.filter_by()
Select.from_statement()
Select.froms
Select.get_children()
Select.get_execution_options()
Select.get_final_froms()
Select.get_label_style()
Select.group_by()
Select.having()
Select.inherit_cache
Select.inner_columns
Select.intersect()
Select.intersect_all()
Select.is_derived_from()
Select.join()
Select.join_from()
Select.label()
Select.lateral()
Select.limit()
Select.offset()
Select.options()
Select.order_by()
Select.outerjoin()
Select.outerjoin_from()
Select.prefix_with()
Select.reduce_columns()
Select.replace_selectable()
Select.scalar_subquery()
Select.select()
Select.select_from()
Select.selected_columns
Select.self_group()
Select.set_label_style()
Select.slice()
Select.subquery()
Select.suffix_with()
Select.union()
Select.union_all()
Select.where()
Select.whereclause
Select.with_for_update()
Select.with_hint()
Select.with_only_columns()
Select.with_statement_hint()
Selectable
SelectBase
SelectBase.add_cte()
SelectBase.alias()
SelectBase.as_scalar()
SelectBase.c
SelectBase.corresponding_column()
SelectBase.cte()
SelectBase.exists()
SelectBase.exported_columns
SelectBase.get_label_style()
SelectBase.inherit_cache
SelectBase.is_derived_from()
SelectBase.label()
SelectBase.lateral()
SelectBase.replace_selectable()
SelectBase.scalar_subquery()
SelectBase.select()
SelectBase.selected_columns
SelectBase.set_label_style()
SelectBase.subquery()
Subquery
TableClause
TableClause.alias()
TableClause.c
TableClause.columns
TableClause.compare()
TableClause.compile()
TableClause.corresponding_column()
TableClause.delete()
TableClause.description
TableClause.entity_namespace
TableClause.exported_columns
TableClause.foreign_keys
TableClause.get_children()
TableClause.implicit_returning
TableClause.inherit_cache
TableClause.insert()
TableClause.is_derived_from()
TableClause.join()
TableClause.lateral()
TableClause.outerjoin()
TableClause.params()
TableClause.primary_key
TableClause.replace_selectable()
TableClause.schema
TableClause.select()
TableClause.self_group()
TableClause.table_valued()
TableClause.tablesample()
TableClause.unique_params()
TableClause.update()
TableSample
TableValuedAlias
TextualSelect
TextualSelect.add_cte()
TextualSelect.alias()
TextualSelect.as_scalar()
TextualSelect.c
TextualSelect.compare()
TextualSelect.compile()
TextualSelect.corresponding_column()
TextualSelect.cte()
TextualSelect.execution_options()
TextualSelect.exists()
TextualSelect.exported_columns
TextualSelect.get_children()
TextualSelect.get_execution_options()
TextualSelect.get_label_style()
TextualSelect.inherit_cache
TextualSelect.is_derived_from()
TextualSelect.label()
TextualSelect.lateral()
TextualSelect.options()
TextualSelect.params()
TextualSelect.replace_selectable()
TextualSelect.scalar_subquery()
TextualSelect.select()
TextualSelect.selected_columns
TextualSelect.self_group()
TextualSelect.set_label_style()
TextualSelect.subquery()
TextualSelect.unique_params()
Values
ScalarValues
- Label Style Constants
SELECT and Related Constructs¶
The term “selectable” refers to any object that represents database rows. In
SQLAlchemy, these objects descend from Selectable
, the
most prominent being Select
, which represents a SQL SELECT
statement. A subset of Selectable
is
FromClause
, which represents objects that can be within
the FROM clause of a Select
statement. A distinguishing feature of
FromClause
is the FromClause.c
attribute, which is a namespace of all the columns contained within the FROM
clause (these elements are themselves ColumnElement
subclasses).
Selectable Foundational Constructors¶
Top level “FROM clause” and “SELECT” constructors.
Object Name | Description |
---|---|
except_(*selects) |
Return an |
except_all(*selects) |
Return an |
exists([__argument]) |
Construct a new |
intersect(*selects) |
Return an |
intersect_all(*selects) |
Return an |
select(*entities, **__kw) |
Construct a new |
table(name, *columns, **kw) |
Produce a new |
union(*selects) |
Return a |
union_all(*selects) |
Return a |
values(*columns, [name, literal_binds]) |
Construct a |
- function sqlalchemy.sql.expression.except_(*selects: _SelectStatementForCompoundArgument) → CompoundSelect¶
Return an
EXCEPT
of multiple selectables.The returned object is an instance of
CompoundSelect
.
- function sqlalchemy.sql.expression.except_all(*selects: _SelectStatementForCompoundArgument) → CompoundSelect¶
Return an
EXCEPT ALL
of multiple selectables.The returned object is an instance of
CompoundSelect
.
- function sqlalchemy.sql.expression.exists(__argument: _ColumnsClauseArgument[Any] | SelectBase | ScalarSelect[Any] | None = None) → Exists¶
Construct a new
Exists
construct.The
exists()
can be invoked by itself to produce anExists
construct, which will accept simple WHERE criteria:exists_criteria = exists().where(table1.c.col1 == table2.c.col2)
However, for greater flexibility in constructing the SELECT, an existing
Select
construct may be converted to anExists
, most conveniently by making use of theSelectBase.exists()
method:exists_criteria = ( select(table2.c.col2).where(table1.c.col1 == table2.c.col2).exists() )
The EXISTS criteria is then used inside of an enclosing SELECT:
stmt = select(table1.c.col1).where(exists_criteria)
The above statement will then be of the form:
SELECT col1 FROM table1 WHERE EXISTS (SELECT table2.col2 FROM table2 WHERE table2.col2 = table1.col1)
See also
EXISTS subqueries - in the 2.0 style tutorial.
SelectBase.exists()
- method to transform aSELECT
to anEXISTS
clause.
- function sqlalchemy.sql.expression.intersect(*selects: _SelectStatementForCompoundArgument) → CompoundSelect¶
Return an
INTERSECT
of multiple selectables.The returned object is an instance of
CompoundSelect
.
- function sqlalchemy.sql.expression.intersect_all(*selects: _SelectStatementForCompoundArgument) → CompoundSelect¶
Return an
INTERSECT ALL
of multiple selectables.The returned object is an instance of
CompoundSelect
.
- function sqlalchemy.sql.expression.select(*entities: _ColumnsClauseArgument[Any], **__kw: Any) → Select[Any]¶
Construct a new
Select
.New in version 1.4: - The
select()
function now accepts column arguments positionally. The top-levelselect()
function will automatically use the 1.x or 2.x style API based on the incoming arguments; usingselect()
from thesqlalchemy.future
module will enforce that only the 2.x style constructor is used.Similar functionality is also available via the
FromClause.select()
method on anyFromClause
.See also
Using SELECT Statements - in the SQLAlchemy Unified Tutorial
- Parameters:
*entities¶ –
Entities to SELECT from. For Core usage, this is typically a series of
ColumnElement
and / orFromClause
objects which will form the columns clause of the resulting statement. For those objects that are instances ofFromClause
(typicallyTable
orAlias
objects), theFromClause.c
collection is extracted to form a collection ofColumnElement
objects.This parameter will also accept
TextClause
constructs as given, as well as ORM-mapped classes.
- function sqlalchemy.sql.expression.table(name: str, *columns: ColumnClause[Any], **kw: Any) → TableClause¶
Produce a new
TableClause
.The object returned is an instance of
TableClause
, which represents the “syntactical” portion of the schema-levelTable
object. It may be used to construct lightweight table constructs.
- function sqlalchemy.sql.expression.union(*selects: _SelectStatementForCompoundArgument) → CompoundSelect¶
Return a
UNION
of multiple selectables.The returned object is an instance of
CompoundSelect
.A similar
union()
method is available on allFromClause
subclasses.
- function sqlalchemy.sql.expression.union_all(*selects: _SelectStatementForCompoundArgument) → CompoundSelect¶
Return a
UNION ALL
of multiple selectables.The returned object is an instance of
CompoundSelect
.A similar
union_all()
method is available on allFromClause
subclasses.
- function sqlalchemy.sql.expression.values(*columns: ColumnClause[Any], name: str | None = None, literal_binds: bool = False) → Values¶
Construct a
Values
construct.The column expressions and the actual data for
Values
are given in two separate steps. The constructor receives the column expressions typically ascolumn()
constructs, and the data is then passed via theValues.data()
method as a list, which can be called multiple times to add more data, e.g.:from sqlalchemy import column from sqlalchemy import values value_expr = values( column("id", Integer), column("name", String), name="my_values", ).data([(1, "name1"), (2, "name2"), (3, "name3")])
- Parameters:
*columns¶ – column expressions, typically composed using
column()
objects.name¶ – the name for this VALUES construct. If omitted, the VALUES construct will be unnamed in a SQL expression. Different backends may have different requirements here.
literal_binds¶ – Defaults to False. Whether or not to render the data values inline in the SQL output, rather than using bound parameters.
Selectable Modifier Constructors¶
Functions listed here are more commonly available as methods from
FromClause
and Selectable
elements, for example,
the alias()
function is usually invoked via the
FromClause.alias()
method.
Object Name | Description |
---|---|
alias(selectable[, name, flat]) |
Return a named alias of the given |
cte(selectable[, name, recursive]) |
Return a new |
join(left, right[, onclause, isouter, ...]) |
Produce a |
lateral(selectable[, name]) |
Return a |
outerjoin(left, right[, onclause, full]) |
Return an |
tablesample(selectable, sampling[, name, seed]) |
Return a |
- function sqlalchemy.sql.expression.alias(selectable: FromClause, name: str | None = None, flat: bool = False) → NamedFromClause¶
Return a named alias of the given
FromClause
.For
Table
andJoin
objects, the return type is theAlias
object. Other kinds ofNamedFromClause
objects may be returned for other kinds ofFromClause
objects.The named alias represents any
FromClause
with an alternate name assigned within SQL, typically using theAS
clause when generated, e.g.SELECT * FROM table AS aliasname
.Equivalent functionality is available via the
FromClause.alias()
method available on allFromClause
objects.- Parameters:
selectable¶ – any
FromClause
subclass, such as a table, select statement, etc.name¶ – string name to be assigned as the alias. If
None
, a name will be deterministically generated at compile time. Deterministic means the name is guaranteed to be unique against other constructs used in the same statement, and will also be the same name for each successive compilation of the same statement object.flat¶ – Will be passed through to if the given selectable is an instance of
Join
- seeJoin.alias()
for details.
- function sqlalchemy.sql.expression.cte(selectable: HasCTE, name: str | None = None, recursive: bool = False) → CTE¶
Return a new
CTE
, or Common Table Expression instance.Please see
HasCTE.cte()
for detail on CTE usage.
- function sqlalchemy.sql.expression.join(left: _FromClauseArgument, right: _FromClauseArgument, onclause: _OnClauseArgument | None = None, isouter: bool = False, full: bool = False) → Join¶
Produce a
Join
object, given twoFromClause
expressions.E.g.:
j = join( user_table, address_table, user_table.c.id == address_table.c.user_id ) stmt = select(user_table).select_from(j)
would emit SQL along the lines of:
SELECT user.id, user.name FROM user JOIN address ON user.id = address.user_id
Similar functionality is available given any
FromClause
object (e.g. such as aTable
) using theFromClause.join()
method.- Parameters:
left¶ – The left side of the join.
right¶ – the right side of the join; this is any
FromClause
object such as aTable
object, and may also be a selectable-compatible object such as an ORM-mapped class.onclause¶ – a SQL expression representing the ON clause of the join. If left at
None
,FromClause.join()
will attempt to join the two tables based on a foreign key relationship.isouter¶ – if True, render a LEFT OUTER JOIN, instead of JOIN.
full¶ – if True, render a FULL OUTER JOIN, instead of JOIN.
See also
FromClause.join()
- method form, based on a given left side.Join
- the type of object produced.
- function sqlalchemy.sql.expression.lateral(selectable: SelectBase | _FromClauseArgument, name: str | None = None) → LateralFromClause¶
Return a
Lateral
object.Lateral
is anAlias
subclass that represents a subquery with the LATERAL keyword applied to it.The special behavior of a LATERAL subquery is that it appears in the FROM clause of an enclosing SELECT, but may correlate to other FROM clauses of that SELECT. It is a special case of subquery only supported by a small number of backends, currently more recent PostgreSQL versions.
See also
LATERAL correlation - overview of usage.
- function sqlalchemy.sql.expression.outerjoin(left: _FromClauseArgument, right: _FromClauseArgument, onclause: _OnClauseArgument | None = None, full: bool = False) → Join¶
Return an
OUTER JOIN
clause element.The returned object is an instance of
Join
.Similar functionality is also available via the
FromClause.outerjoin()
method on anyFromClause
.- Parameters:
To chain joins together, use the
FromClause.join()
orFromClause.outerjoin()
methods on the resultingJoin
object.
- function sqlalchemy.sql.expression.tablesample(selectable: _FromClauseArgument, sampling: float | Function[Any], name: str | None = None, seed: roles.ExpressionElementRole[Any] | None = None) → TableSample¶
Return a
TableSample
object.TableSample
is anAlias
subclass that represents a table with the TABLESAMPLE clause applied to it.tablesample()
is also available from theFromClause
class via theFromClause.tablesample()
method.The TABLESAMPLE clause allows selecting a randomly selected approximate percentage of rows from a table. It supports multiple sampling methods, most commonly BERNOULLI and SYSTEM.
e.g.:
from sqlalchemy import func selectable = people.tablesample( func.bernoulli(1), name="alias", seed=func.random() ) stmt = select(selectable.c.people_id)
Assuming
people
with a columnpeople_id
, the above statement would render as:SELECT alias.people_id FROM people AS alias TABLESAMPLE bernoulli(:bernoulli_1) REPEATABLE (random())
Selectable Class Documentation¶
The classes here are generated using the constructors listed at Selectable Foundational Constructors and Selectable Modifier Constructors.
Object Name | Description |
---|---|
Represents an table or selectable alias (AS). |
|
Base class of aliases against tables, subqueries, and other selectables. |
|
Forms the basis of |
|
Represent a Common Table Expression. |
|
Mark a |
|
Represent an |
|
Represent an element that can be used within the |
|
Base class for SELECT statements where additional elements can be added. |
|
Mixin that declares a class to include CTE support. |
|
Represent a |
|
Represent a LATERAL subquery. |
|
The base-most class for Core constructs that have some concept of columns that can represent rows. |
|
Represent a scalar subquery. |
|
Represent a scalar |
|
Represents a |
|
Mark a class as being selectable. |
|
Base class for SELECT statements. |
|
Represent a subquery of a SELECT. |
|
Represents a minimal “table” construct. |
|
Represent a TABLESAMPLE clause. |
|
An alias against a “table valued” SQL function. |
|
Wrap a |
|
Represent a |
- class sqlalchemy.sql.expression.Alias¶
Represents an table or selectable alias (AS).
Represents an alias, as typically applied to any table or sub-select within a SQL statement using the
AS
keyword (or without the keyword on certain databases such as Oracle Database).This object is constructed from the
alias()
module level function as well as theFromClause.alias()
method available on allFromClause
subclasses.See also
Members
Class signature
class
sqlalchemy.sql.expression.Alias
(sqlalchemy.sql.roles.DMLTableRole
,sqlalchemy.sql.expression.FromClauseAlias
)-
attribute
sqlalchemy.sql.expression.Alias.
inherit_cache: bool | None = True¶ Indicate if this
HasCacheKey
instance should make use of the cache key generation scheme used by its immediate superclass.The attribute defaults to
None
, which indicates that a construct has not yet taken into account whether or not its appropriate for it to participate in caching; this is functionally equivalent to setting the value toFalse
, except that a warning is also emitted.This flag can be set to
True
on a particular class, if the SQL that corresponds to the object does not change based on attributes which are local to this class, and not its superclass.See also
Enabling Caching Support for Custom Constructs - General guideslines for setting the
HasCacheKey.inherit_cache
attribute for third-party or user defined SQL constructs.
-
attribute
- class sqlalchemy.sql.expression.AliasedReturnsRows¶
Base class of aliases against tables, subqueries, and other selectables.
Members
Class signature
class
sqlalchemy.sql.expression.AliasedReturnsRows
(sqlalchemy.sql.expression.NoInit
,sqlalchemy.sql.expression.NamedFromClause
)-
attribute
sqlalchemy.sql.expression.AliasedReturnsRows.
description¶
-
method
sqlalchemy.sql.expression.AliasedReturnsRows.
is_derived_from(fromclause: FromClause | None) → bool¶ Return
True
if thisFromClause
is ‘derived’ from the givenFromClause
.An example would be an Alias of a Table is derived from that Table.
-
attribute
sqlalchemy.sql.expression.AliasedReturnsRows.
original¶ Legacy for dialects that are referring to Alias.original.
-
attribute
- class sqlalchemy.sql.expression.CompoundSelect¶
Forms the basis of
UNION
,UNION ALL
, and other SELECT-based set operations.Members
add_cte(), alias(), as_scalar(), c, corresponding_column(), cte(), execution_options(), exists(), exported_columns, fetch(), get_execution_options(), get_label_style(), group_by(), is_derived_from(), label(), lateral(), limit(), offset(), options(), order_by(), replace_selectable(), scalar_subquery(), select(), selected_columns, self_group(), set_label_style(), slice(), subquery(), with_for_update()
Class signature
class
sqlalchemy.sql.expression.CompoundSelect
(sqlalchemy.sql.expression.HasCompileState
,sqlalchemy.sql.expression.GenerativeSelect
,sqlalchemy.sql.expression.ExecutableReturnsRows
)-
method
sqlalchemy.sql.expression.CompoundSelect.
add_cte(*ctes: CTE, nest_here: bool = False) → Self¶ inherited from the
HasCTE.add_cte()
method ofHasCTE
Add one or more
CTE
constructs to this statement.This method will associate the given
CTE
constructs with the parent statement such that they will each be unconditionally rendered in the WITH clause of the final statement, even if not referenced elsewhere within the statement or any sub-selects.The optional
HasCTE.add_cte.nest_here
parameter when set to True will have the effect that each givenCTE
will render in a WITH clause rendered directly along with this statement, rather than being moved to the top of the ultimate rendered statement, even if this statement is rendered as a subquery within a larger statement.This method has two general uses. One is to embed CTE statements that serve some purpose without being referenced explicitly, such as the use case of embedding a DML statement such as an INSERT or UPDATE as a CTE inline with a primary statement that may draw from its results indirectly. The other is to provide control over the exact placement of a particular series of CTE constructs that should remain rendered directly in terms of a particular statement that may be nested in a larger statement.
E.g.:
from sqlalchemy import table, column, select t = table("t", column("c1"), column("c2")) ins = t.insert().values({"c1": "x", "c2": "y"}).cte() stmt = select(t).add_cte(ins)
Would render:
WITH anon_1 AS ( INSERT INTO t (c1, c2) VALUES (:param_1, :param_2) ) SELECT t.c1, t.c2 FROM t
Above, the “anon_1” CTE is not referenced in the SELECT statement, however still accomplishes the task of running an INSERT statement.
Similarly in a DML-related context, using the PostgreSQL
Insert
construct to generate an “upsert”:from sqlalchemy import table, column from sqlalchemy.dialects.postgresql import insert t = table("t", column("c1"), column("c2")) delete_statement_cte = t.delete().where(t.c.c1 < 1).cte("deletions") insert_stmt = insert(t).values({"c1": 1, "c2": 2}) update_statement = insert_stmt.on_conflict_do_update( index_elements=[t.c.c1], set_={ "c1": insert_stmt.excluded.c1, "c2": insert_stmt.excluded.c2, }, ).add_cte(delete_statement_cte) print(update_statement)
The above statement renders as:
WITH deletions AS ( DELETE FROM t WHERE t.c1 < %(c1_1)s ) INSERT INTO t (c1, c2) VALUES (%(c1)s, %(c2)s) ON CONFLICT (c1) DO UPDATE SET c1 = excluded.c1, c2 = excluded.c2
New in version 1.4.21.
- Parameters:
*ctes¶ –
zero or more
CTE
constructs.Changed in version 2.0: Multiple CTE instances are accepted
nest_here¶ –
if True, the given CTE or CTEs will be rendered as though they specified the
HasCTE.cte.nesting
flag toTrue
when they were added to thisHasCTE
. Assuming the given CTEs are not referenced in an outer-enclosing statement as well, the CTEs given should render at the level of this statement when this flag is given.New in version 2.0.
See also
-
method
sqlalchemy.sql.expression.CompoundSelect.
alias(name: str | None = None, flat: bool = False) → Subquery¶ inherited from the
SelectBase.alias()
method ofSelectBase
Return a named subquery against this
SelectBase
.For a
SelectBase
(as opposed to aFromClause
), this returns aSubquery
object which behaves mostly the same as theAlias
object that is used with aFromClause
.Changed in version 1.4: The
SelectBase.alias()
method is now a synonym for theSelectBase.subquery()
method.
-
method
sqlalchemy.sql.expression.CompoundSelect.
as_scalar() → ScalarSelect[Any]¶ inherited from the
SelectBase.as_scalar()
method ofSelectBase
Deprecated since version 1.4: The
SelectBase.as_scalar()
method is deprecated and will be removed in a future release. Please refer toSelectBase.scalar_subquery()
.
-
attribute
sqlalchemy.sql.expression.CompoundSelect.
c¶ inherited from the
SelectBase.c
attribute ofSelectBase
Deprecated since version 1.4: The
SelectBase.c
andSelectBase.columns
attributes are deprecated and will be removed in a future release; these attributes implicitly create a subquery that should be explicit. Please callSelectBase.subquery()
first in order to create a subquery, which then contains this attribute. To access the columns that this SELECT object SELECTs from, use theSelectBase.selected_columns
attribute.
-
method
sqlalchemy.sql.expression.CompoundSelect.
corresponding_column(column: KeyedColumnElement[Any], require_embedded: bool = False) → KeyedColumnElement[Any] | None¶ inherited from the
Selectable.corresponding_column()
method ofSelectable
Given a
ColumnElement
, return the exportedColumnElement
object from theSelectable.exported_columns
collection of thisSelectable
which corresponds to that originalColumnElement
via a common ancestor column.- Parameters:
column¶ – the target
ColumnElement
to be matched.require_embedded¶ – only return corresponding columns for the given
ColumnElement
, if the givenColumnElement
is actually present within a sub-element of thisSelectable
. Normally the column will match if it merely shares a common ancestor with one of the exported columns of thisSelectable
.
See also
Selectable.exported_columns
- theColumnCollection
that is used for the operation.ColumnCollection.corresponding_column()
- implementation method.
-
method
sqlalchemy.sql.expression.CompoundSelect.
cte(name: str | None = None, recursive: bool = False, nesting: bool = False) → CTE¶ inherited from the
HasCTE.cte()
method ofHasCTE
Return a new
CTE
, or Common Table Expression instance.Common table expressions are a SQL standard whereby SELECT statements can draw upon secondary statements specified along with the primary statement, using a clause called “WITH”. Special semantics regarding UNION can also be employed to allow “recursive” queries, where a SELECT statement can draw upon the set of rows that have previously been selected.
CTEs can also be applied to DML constructs UPDATE, INSERT and DELETE on some databases, both as a source of CTE rows when combined with RETURNING, as well as a consumer of CTE rows.
SQLAlchemy detects
CTE
objects, which are treated similarly toAlias
objects, as special elements to be delivered to the FROM clause of the statement as well as to a WITH clause at the top of the statement.For special prefixes such as PostgreSQL “MATERIALIZED” and “NOT MATERIALIZED”, the
CTE.prefix_with()
method may be used to establish these.Changed in version 1.3.13: Added support for prefixes. In particular - MATERIALIZED and NOT MATERIALIZED.
- Parameters:
name¶ – name given to the common table expression. Like
FromClause.alias()
, the name can be left asNone
in which case an anonymous symbol will be used at query compile time.recursive¶ – if
True
, will renderWITH RECURSIVE
. A recursive common table expression is intended to be used in conjunction with UNION ALL in order to derive rows from those already selected.nesting¶ –
if
True
, will render the CTE locally to the statement in which it is referenced. For more complex scenarios, theHasCTE.add_cte()
method using theHasCTE.add_cte.nest_here
parameter may also be used to more carefully control the exact placement of a particular CTE.New in version 1.4.24.
See also
The following examples include two from PostgreSQL’s documentation at https://www.postgresql.org/docs/current/static/queries-with.html, as well as additional examples.
Example 1, non recursive:
from sqlalchemy import ( Table, Column, String, Integer, MetaData, select, func, ) metadata = MetaData() orders = Table( "orders", metadata, Column("region", String), Column("amount", Integer), Column("product", String), Column("quantity", Integer), ) regional_sales = ( select(orders.c.region, func.sum(orders.c.amount).label("total_sales")) .group_by(orders.c.region) .cte("regional_sales") ) top_regions = ( select(regional_sales.c.region) .where( regional_sales.c.total_sales > select(func.sum(regional_sales.c.total_sales) / 10) ) .cte("top_regions") ) statement = ( select( orders.c.region, orders.c.product, func.sum(orders.c.quantity).label("product_units"), func.sum(orders.c.amount).label("product_sales"), ) .where(orders.c.region.in_(select(top_regions.c.region))) .group_by(orders.c.region, orders.c.product) ) result = conn.execute(statement).fetchall()
Example 2, WITH RECURSIVE:
from sqlalchemy import ( Table, Column, String, Integer, MetaData, select, func, ) metadata = MetaData() parts = Table( "parts", metadata, Column("part", String), Column("sub_part", String), Column("quantity", Integer), ) included_parts = ( select(parts.c.sub_part, parts.c.part, parts.c.quantity) .where(parts.c.part == "our part") .cte(recursive=True) ) incl_alias = included_parts.alias() parts_alias = parts.alias() included_parts = included_parts.union_all( select( parts_alias.c.sub_part, parts_alias.c.part, parts_alias.c.quantity ).where(parts_alias.c.part == incl_alias.c.sub_part) ) statement = select( included_parts.c.sub_part, func.sum(included_parts.c.quantity).label("total_quantity"), ).group_by(included_parts.c.sub_part) result = conn.execute(statement).fetchall()
Example 3, an upsert using UPDATE and INSERT with CTEs:
from datetime import date from sqlalchemy import ( MetaData, Table, Column, Integer, Date, select, literal, and_, exists, ) metadata = MetaData() visitors = Table( "visitors", metadata, Column("product_id", Integer, primary_key=True), Column("date", Date, primary_key=True), Column("count", Integer), ) # add 5 visitors for the product_id == 1 product_id = 1 day = date.today() count = 5 update_cte = ( visitors.update() .where( and_(visitors.c.product_id == product_id, visitors.c.date == day) ) .values(count=visitors.c.count + count) .returning(literal(1)) .cte("update_cte") ) upsert = visitors.insert().from_select( [visitors.c.product_id, visitors.c.date, visitors.c.count], select(literal(product_id), literal(day), literal(count)).where( ~exists(update_cte.select()) ), ) connection.execute(upsert)
Example 4, Nesting CTE (SQLAlchemy 1.4.24 and above):
value_a = select(literal("root").label("n")).cte("value_a") # A nested CTE with the same name as the root one value_a_nested = select(literal("nesting").label("n")).cte( "value_a", nesting=True ) # Nesting CTEs takes ascendency locally # over the CTEs at a higher level value_b = select(value_a_nested.c.n).cte("value_b") value_ab = select(value_a.c.n.label("a"), value_b.c.n.label("b"))
The above query will render the second CTE nested inside the first, shown with inline parameters below as:
WITH value_a AS (SELECT 'root' AS n), value_b AS (WITH value_a AS (SELECT 'nesting' AS n) SELECT value_a.n AS n FROM value_a) SELECT value_a.n AS a, value_b.n AS b FROM value_a, value_b
The same CTE can be set up using the
HasCTE.add_cte()
method as follows (SQLAlchemy 2.0 and above):value_a = select(literal("root").label("n")).cte("value_a") # A nested CTE with the same name as the root one value_a_nested = select(literal("nesting").label("n")).cte("value_a") # Nesting CTEs takes ascendency locally # over the CTEs at a higher level value_b = ( select(value_a_nested.c.n) .add_cte(value_a_nested, nest_here=True) .cte("value_b") ) value_ab = select(value_a.c.n.label("a"), value_b.c.n.label("b"))
Example 5, Non-Linear CTE (SQLAlchemy 1.4.28 and above):
edge = Table( "edge", metadata, Column("id", Integer, primary_key=True), Column("left", Integer), Column("right", Integer), ) root_node = select(literal(1).label("node")).cte("nodes", recursive=True) left_edge = select(edge.c.left).join( root_node, edge.c.right == root_node.c.node ) right_edge = select(edge.c.right).join( root_node, edge.c.left == root_node.c.node ) subgraph_cte = root_node.union(left_edge, right_edge) subgraph = select(subgraph_cte)
The above query will render 2 UNIONs inside the recursive CTE:
WITH RECURSIVE nodes(node) AS ( SELECT 1 AS node UNION SELECT edge."left" AS "left" FROM edge JOIN nodes ON edge."right" = nodes.node UNION SELECT edge."right" AS "right" FROM edge JOIN nodes ON edge."left" = nodes.node ) SELECT nodes.node FROM nodes
See also
Query.cte()
- ORM version ofHasCTE.cte()
.
-
method
sqlalchemy.sql.expression.CompoundSelect.
execution_options(**kw: Any) → Self¶ inherited from the
Executable.execution_options()
method ofExecutable
Set non-SQL options for the statement which take effect during execution.
Execution options can be set at many scopes, including per-statement, per-connection, or per execution, using methods such as
Connection.execution_options()
and parameters which accept a dictionary of options such asConnection.execute.execution_options
andSession.execute.execution_options
.The primary characteristic of an execution option, as opposed to other kinds of options such as ORM loader options, is that execution options never affect the compiled SQL of a query, only things that affect how the SQL statement itself is invoked or how results are fetched. That is, execution options are not part of what’s accommodated by SQL compilation nor are they considered part of the cached state of a statement.
The
Executable.execution_options()
method is generative, as is the case for the method as applied to theEngine
andQuery
objects, which means when the method is called, a copy of the object is returned, which applies the given parameters to that new copy, but leaves the original unchanged:statement = select(table.c.x, table.c.y) new_statement = statement.execution_options(my_option=True)
An exception to this behavior is the
Connection
object, where theConnection.execution_options()
method is explicitly not generative.The kinds of options that may be passed to
Executable.execution_options()
and other related methods and parameter dictionaries include parameters that are explicitly consumed by SQLAlchemy Core or ORM, as well as arbitrary keyword arguments not defined by SQLAlchemy, which means the methods and/or parameter dictionaries may be used for user-defined parameters that interact with custom code, which may access the parameters using methods such asExecutable.get_execution_options()
andConnection.get_execution_options()
, or within selected event hooks using a dedicatedexecution_options
event parameter such asConnectionEvents.before_execute.execution_options
orORMExecuteState.execution_options
, e.g.:from sqlalchemy import event @event.listens_for(some_engine, "before_execute") def _process_opt(conn, statement, multiparams, params, execution_options): "run a SQL function before invoking a statement" if execution_options.get("do_special_thing", False): conn.exec_driver_sql("run_special_function()")
Within the scope of options that are explicitly recognized by SQLAlchemy, most apply to specific classes of objects and not others. The most common execution options include:
Connection.execution_options.isolation_level
- sets the isolation level for a connection or a class of connections via anEngine
. This option is accepted only byConnection
orEngine
.Connection.execution_options.stream_results
- indicates results should be fetched using a server side cursor; this option is accepted byConnection
, by theConnection.execute.execution_options
parameter onConnection.execute()
, and additionally byExecutable.execution_options()
on a SQL statement object, as well as by ORM constructs likeSession.execute()
.Connection.execution_options.compiled_cache
- indicates a dictionary that will serve as the SQL compilation cache for aConnection
orEngine
, as well as for ORM methods likeSession.execute()
. Can be passed asNone
to disable caching for statements. This option is not accepted byExecutable.execution_options()
as it is inadvisable to carry along a compilation cache within a statement object.Connection.execution_options.schema_translate_map
- a mapping of schema names used by the Schema Translate Map feature, accepted byConnection
,Engine
,Executable
, as well as by ORM constructs likeSession.execute()
.
See also
Connection.execution_options()
Connection.execute.execution_options
Session.execute.execution_options
ORM Execution Options - documentation on all ORM-specific execution options
-
method
sqlalchemy.sql.expression.CompoundSelect.
exists() → Exists¶ inherited from the
SelectBase.exists()
method ofSelectBase
Return an
Exists
representation of this selectable, which can be used as a column expression.The returned object is an instance of
Exists
.New in version 1.4.
-
attribute
sqlalchemy.sql.expression.CompoundSelect.
exported_columns¶ inherited from the
SelectBase.exported_columns
attribute ofSelectBase
A
ColumnCollection
that represents the “exported” columns of thisSelectable
, not includingTextClause
constructs.The “exported” columns for a
SelectBase
object are synonymous with theSelectBase.selected_columns
collection.New in version 1.4.
-
method
sqlalchemy.sql.expression.CompoundSelect.
fetch(count: _LimitOffsetType, with_ties: bool = False, percent: bool = False) → Self¶ inherited from the
GenerativeSelect.fetch()
method ofGenerativeSelect
Return a new selectable with the given FETCH FIRST criterion applied.
This is a numeric value which usually renders as
FETCH {FIRST | NEXT} [ count ] {ROW | ROWS} {ONLY | WITH TIES}
expression in the resulting select. This functionality is is currently implemented for Oracle Database, PostgreSQL, MSSQL.Use
GenerativeSelect.offset()
to specify the offset.Note
The
GenerativeSelect.fetch()
method will replace any clause applied withGenerativeSelect.limit()
.New in version 1.4.
- Parameters:
count¶ – an integer COUNT parameter, or a SQL expression that provides an integer result. When
percent=True
this will represent the percentage of rows to return, not the absolute value. PassNone
to reset it.with_ties¶ – When
True
, the WITH TIES option is used to return any additional rows that tie for the last place in the result set according to theORDER BY
clause. TheORDER BY
may be mandatory in this case. Defaults toFalse
percent¶ – When
True
,count
represents the percentage of the total number of selected rows to return. Defaults toFalse
-
method
sqlalchemy.sql.expression.CompoundSelect.
get_execution_options() → _ExecuteOptions¶ inherited from the
Executable.get_execution_options()
method ofExecutable
Get the non-SQL options which will take effect during execution.
New in version 1.3.
See also
-
method
sqlalchemy.sql.expression.CompoundSelect.
get_label_style() → SelectLabelStyle¶ inherited from the
GenerativeSelect.get_label_style()
method ofGenerativeSelect
Retrieve the current label style.
New in version 1.4.
-
method
sqlalchemy.sql.expression.CompoundSelect.
group_by(_GenerativeSelect__first: Literal[None, _NoArg.NO_ARG] | _ColumnExpressionOrStrLabelArgument[Any] = _NoArg.NO_ARG, *clauses: _ColumnExpressionOrStrLabelArgument[Any]) → Self¶ inherited from the
GenerativeSelect.group_by()
method ofGenerativeSelect
Return a new selectable with the given list of GROUP BY criterion applied.
All existing GROUP BY settings can be suppressed by passing
None
.e.g.:
stmt = select(table.c.name, func.max(table.c.stat)).group_by(table.c.name)
- Parameters:
*clauses¶ – a series of
ColumnElement
constructs which will be used to generate an GROUP BY clause.
-
method
sqlalchemy.sql.expression.CompoundSelect.
is_derived_from(fromclause: FromClause | None) → bool¶ Return
True
if thisReturnsRows
is ‘derived’ from the givenFromClause
.An example would be an Alias of a Table is derived from that Table.
-
method
sqlalchemy.sql.expression.CompoundSelect.
label(name: str | None) → Label[Any]¶ inherited from the
SelectBase.label()
method ofSelectBase
Return a ‘scalar’ representation of this selectable, embedded as a subquery with a label.
See also
-
method
sqlalchemy.sql.expression.CompoundSelect.
lateral(name: str | None = None) → LateralFromClause¶ inherited from the
SelectBase.lateral()
method ofSelectBase
Return a LATERAL alias of this
Selectable
.The return value is the
Lateral
construct also provided by the top-levellateral()
function.See also
LATERAL correlation - overview of usage.
-
method
sqlalchemy.sql.expression.CompoundSelect.
limit(limit: _LimitOffsetType) → Self¶ inherited from the
GenerativeSelect.limit()
method ofGenerativeSelect
Return a new selectable with the given LIMIT criterion applied.
This is a numerical value which usually renders as a
LIMIT
expression in the resulting select. Backends that don’t supportLIMIT
will attempt to provide similar functionality.Note
The
GenerativeSelect.limit()
method will replace any clause applied withGenerativeSelect.fetch()
.- Parameters:
limit¶ – an integer LIMIT parameter, or a SQL expression that provides an integer result. Pass
None
to reset it.
-
method
sqlalchemy.sql.expression.CompoundSelect.
offset(offset: _LimitOffsetType) → Self¶ inherited from the
GenerativeSelect.offset()
method ofGenerativeSelect
Return a new selectable with the given OFFSET criterion applied.
This is a numeric value which usually renders as an
OFFSET
expression in the resulting select. Backends that don’t supportOFFSET
will attempt to provide similar functionality.- Parameters:
offset¶ – an integer OFFSET parameter, or a SQL expression that provides an integer result. Pass
None
to reset it.
-
method
sqlalchemy.sql.expression.CompoundSelect.
options(*options: ExecutableOption) → Self¶ inherited from the
Executable.options()
method ofExecutable
Apply options to this statement.
In the general sense, options are any kind of Python object that can be interpreted by the SQL compiler for the statement. These options can be consumed by specific dialects or specific kinds of compilers.
The most commonly known kind of option are the ORM level options that apply “eager load” and other loading behaviors to an ORM query. However, options can theoretically be used for many other purposes.
For background on specific kinds of options for specific kinds of statements, refer to the documentation for those option objects.
Changed in version 1.4: - added
Executable.options()
to Core statement objects towards the goal of allowing unified Core / ORM querying capabilities.See also
Column Loading Options - refers to options specific to the usage of ORM queries
Relationship Loading with Loader Options - refers to options specific to the usage of ORM queries
-
method
sqlalchemy.sql.expression.CompoundSelect.
order_by(_GenerativeSelect__first: Literal[None, _NoArg.NO_ARG] | _ColumnExpressionOrStrLabelArgument[Any] = _NoArg.NO_ARG, *clauses: _ColumnExpressionOrStrLabelArgument[Any]) → Self¶ inherited from the
GenerativeSelect.order_by()
method ofGenerativeSelect
Return a new selectable with the given list of ORDER BY criteria applied.
e.g.:
stmt = select(table).order_by(table.c.id, table.c.name)
Calling this method multiple times is equivalent to calling it once with all the clauses concatenated. All existing ORDER BY criteria may be cancelled by passing
None
by itself. New ORDER BY criteria may then be added by invokingQuery.order_by()
again, e.g.:# will erase all ORDER BY and ORDER BY new_col alone stmt = stmt.order_by(None).order_by(new_col)
- Parameters:
*clauses¶ – a series of
ColumnElement
constructs which will be used to generate an ORDER BY clause.
See also
ORDER BY - in the SQLAlchemy Unified Tutorial
Ordering or Grouping by a Label - in the SQLAlchemy Unified Tutorial
-
method
sqlalchemy.sql.expression.CompoundSelect.
replace_selectable(old: FromClause, alias: Alias) → Self¶ inherited from the
Selectable.replace_selectable()
method ofSelectable
Replace all occurrences of
FromClause
‘old’ with the givenAlias
object, returning a copy of thisFromClause
.Deprecated since version 1.4: The
Selectable.replace_selectable()
method is deprecated, and will be removed in a future release. Similar functionality is available via the sqlalchemy.sql.visitors module.
-
method
sqlalchemy.sql.expression.CompoundSelect.
scalar_subquery() → ScalarSelect[Any]¶ inherited from the
SelectBase.scalar_subquery()
method ofSelectBase
Return a ‘scalar’ representation of this selectable, which can be used as a column expression.
The returned object is an instance of
ScalarSelect
.Typically, a select statement which has only one column in its columns clause is eligible to be used as a scalar expression. The scalar subquery can then be used in the WHERE clause or columns clause of an enclosing SELECT.
Note that the scalar subquery differentiates from the FROM-level subquery that can be produced using the
SelectBase.subquery()
method.See also
Scalar and Correlated Subqueries - in the 2.0 tutorial
-
method
sqlalchemy.sql.expression.CompoundSelect.
select(*arg: Any, **kw: Any) → Select¶ inherited from the
SelectBase.select()
method ofSelectBase
Deprecated since version 1.4: The
SelectBase.select()
method is deprecated and will be removed in a future release; this method implicitly creates a subquery that should be explicit. Please callSelectBase.subquery()
first in order to create a subquery, which then can be selected.
-
attribute
sqlalchemy.sql.expression.CompoundSelect.
selected_columns¶ A
ColumnCollection
representing the columns that this SELECT statement or similar construct returns in its result set, not includingTextClause
constructs.For a
CompoundSelect
, theCompoundSelect.selected_columns
attribute returns the selected columns of the first SELECT statement contained within the series of statements within the set operation.See also
New in version 1.4.
-
method
sqlalchemy.sql.expression.CompoundSelect.
self_group(against: OperatorType | None = None) → GroupedElement¶ Apply a ‘grouping’ to this
ClauseElement
.This method is overridden by subclasses to return a “grouping” construct, i.e. parenthesis. In particular it’s used by “binary” expressions to provide a grouping around themselves when placed into a larger expression, as well as by
select()
constructs when placed into the FROM clause of anotherselect()
. (Note that subqueries should be normally created using theSelect.alias()
method, as many platforms require nested SELECT statements to be named).As expressions are composed together, the application of
self_group()
is automatic - end-user code should never need to use this method directly. Note that SQLAlchemy’s clause constructs take operator precedence into account - so parenthesis might not be needed, for example, in an expression likex OR (y AND z)
- AND takes precedence over OR.The base
self_group()
method ofClauseElement
just returns self.
-
method
sqlalchemy.sql.expression.CompoundSelect.
set_label_style(style: SelectLabelStyle) → CompoundSelect¶ Return a new selectable with the specified label style.
There are three “label styles” available,
SelectLabelStyle.LABEL_STYLE_DISAMBIGUATE_ONLY
,SelectLabelStyle.LABEL_STYLE_TABLENAME_PLUS_COL
, andSelectLabelStyle.LABEL_STYLE_NONE
. The default style isSelectLabelStyle.LABEL_STYLE_DISAMBIGUATE_ONLY
.In modern SQLAlchemy, there is not generally a need to change the labeling style, as per-expression labels are more effectively used by making use of the
ColumnElement.label()
method. In past versions,LABEL_STYLE_TABLENAME_PLUS_COL
was used to disambiguate same-named columns from different tables, aliases, or subqueries; the newerLABEL_STYLE_DISAMBIGUATE_ONLY
now applies labels only to names that conflict with an existing name so that the impact of this labeling is minimal.The rationale for disambiguation is mostly so that all column expressions are available from a given
FromClause.c
collection when a subquery is created.New in version 1.4: - the
GenerativeSelect.set_label_style()
method replaces the previous combination of.apply_labels()
,.with_labels()
anduse_labels=True
methods and/or parameters.See also
LABEL_STYLE_DISAMBIGUATE_ONLY
LABEL_STYLE_TABLENAME_PLUS_COL
LABEL_STYLE_NONE
LABEL_STYLE_DEFAULT
-
method
sqlalchemy.sql.expression.CompoundSelect.
slice(start: int, stop: int) → Self¶ inherited from the
GenerativeSelect.slice()
method ofGenerativeSelect
Apply LIMIT / OFFSET to this statement based on a slice.
The start and stop indices behave like the argument to Python’s built-in
range()
function. This method provides an alternative to usingLIMIT
/OFFSET
to get a slice of the query.For example,
stmt = select(User).order_by(User.id).slice(1, 3)
renders as
SELECT users.id AS users_id, users.name AS users_name FROM users ORDER BY users.id LIMIT ? OFFSET ? (2, 1)
Note
The
GenerativeSelect.slice()
method will replace any clause applied withGenerativeSelect.fetch()
.New in version 1.4: Added the
GenerativeSelect.slice()
method generalized from the ORM.
-
method
sqlalchemy.sql.expression.CompoundSelect.
subquery(name: str | None = None) → Subquery¶ inherited from the
SelectBase.subquery()
method ofSelectBase
Return a subquery of this
SelectBase
.A subquery is from a SQL perspective a parenthesized, named construct that can be placed in the FROM clause of another SELECT statement.
Given a SELECT statement such as:
stmt = select(table.c.id, table.c.name)
The above statement might look like:
SELECT table.id, table.name FROM table
The subquery form by itself renders the same way, however when embedded into the FROM clause of another SELECT statement, it becomes a named sub-element:
subq = stmt.subquery() new_stmt = select(subq)
The above renders as:
SELECT anon_1.id, anon_1.name FROM (SELECT table.id, table.name FROM table) AS anon_1
Historically,
SelectBase.subquery()
is equivalent to calling theFromClause.alias()
method on a FROM object; however, as aSelectBase
object is not directly FROM object, theSelectBase.subquery()
method provides clearer semantics.New in version 1.4.
-
method
sqlalchemy.sql.expression.CompoundSelect.
with_for_update(*, nowait: bool = False, read: bool = False, of: _ForUpdateOfArgument | None = None, skip_locked: bool = False, key_share: bool = False) → Self¶ inherited from the
GenerativeSelect.with_for_update()
method ofGenerativeSelect
Specify a
FOR UPDATE
clause for thisGenerativeSelect
.E.g.:
stmt = select(table).with_for_update(nowait=True)
On a database like PostgreSQL or Oracle Database, the above would render a statement like:
SELECT table.a, table.b FROM table FOR UPDATE NOWAIT
on other backends, the
nowait
option is ignored and instead would produce:SELECT table.a, table.b FROM table FOR UPDATE
When called with no arguments, the statement will render with the suffix
FOR UPDATE
. Additional arguments can then be provided which allow for common database-specific variants.- Parameters:
nowait¶ – boolean; will render
FOR UPDATE NOWAIT
on Oracle Database and PostgreSQL dialects.read¶ – boolean; will render
LOCK IN SHARE MODE
on MySQL,FOR SHARE
on PostgreSQL. On PostgreSQL, when combined withnowait
, will renderFOR SHARE NOWAIT
.of¶ – SQL expression or list of SQL expression elements, (typically
Column
objects or a compatible expression, for some backends may also be a table expression) which will render into aFOR UPDATE OF
clause; supported by PostgreSQL, Oracle Database, some MySQL versions and possibly others. May render as a table or as a column depending on backend.skip_locked¶ – boolean, will render
FOR UPDATE SKIP LOCKED
on Oracle Database and PostgreSQL dialects orFOR SHARE SKIP LOCKED
ifread=True
is also specified.key_share¶ – boolean, will render
FOR NO KEY UPDATE
, or if combined withread=True
will renderFOR KEY SHARE
, on the PostgreSQL dialect.
-
method
- class sqlalchemy.sql.expression.CTE¶
Represent a Common Table Expression.
The
CTE
object is obtained using theSelectBase.cte()
method from any SELECT statement. A less often available syntax also allows use of theHasCTE.cte()
method present on DML constructs such asInsert
,Update
andDelete
. See theHasCTE.cte()
method for usage details on CTEs.Members
Class signature
class
sqlalchemy.sql.expression.CTE
(sqlalchemy.sql.roles.DMLTableRole
,sqlalchemy.sql.roles.IsCTERole
,sqlalchemy.sql.expression.Generative
,sqlalchemy.sql.expression.HasPrefixes
,sqlalchemy.sql.expression.HasSuffixes
,sqlalchemy.sql.expression.AliasedReturnsRows
)-
method
sqlalchemy.sql.expression.CTE.
alias(name: str | None = None, flat: bool = False) → CTE¶ -
This method is a CTE-specific specialization of the
FromClause.alias()
method.
-
method
sqlalchemy.sql.expression.CTE.
union(*other: _SelectStatementForCompoundArgument) → CTE¶ Return a new
CTE
with a SQLUNION
of the original CTE against the given selectables provided as positional arguments.- Parameters:
*other¶ –
one or more elements with which to create a UNION.
Changed in version 1.4.28: multiple elements are now accepted.
See also
HasCTE.cte()
- examples of calling styles
-
method
sqlalchemy.sql.expression.CTE.
union_all(*other: _SelectStatementForCompoundArgument) → CTE¶ Return a new
CTE
with a SQLUNION ALL
of the original CTE against the given selectables provided as positional arguments.- Parameters:
*other¶ –
one or more elements with which to create a UNION.
Changed in version 1.4.28: multiple elements are now accepted.
See also
HasCTE.cte()
- examples of calling styles
-
method
- class sqlalchemy.sql.expression.Executable¶
Mark a
ClauseElement
as supporting execution.Executable
is a superclass for all “statement” types of objects, includingselect()
,delete()
,update()
,insert()
,text()
.Class signature
class
sqlalchemy.sql.expression.Executable
(sqlalchemy.sql.roles.StatementRole
)-
method
sqlalchemy.sql.expression.Executable.
execution_options(**kw: Any) → Self¶ Set non-SQL options for the statement which take effect during execution.
Execution options can be set at many scopes, including per-statement, per-connection, or per execution, using methods such as
Connection.execution_options()
and parameters which accept a dictionary of options such asConnection.execute.execution_options
andSession.execute.execution_options
.The primary characteristic of an execution option, as opposed to other kinds of options such as ORM loader options, is that execution options never affect the compiled SQL of a query, only things that affect how the SQL statement itself is invoked or how results are fetched. That is, execution options are not part of what’s accommodated by SQL compilation nor are they considered part of the cached state of a statement.
The
Executable.execution_options()
method is generative, as is the case for the method as applied to theEngine
andQuery
objects, which means when the method is called, a copy of the object is returned, which applies the given parameters to that new copy, but leaves the original unchanged:statement = select(table.c.x, table.c.y) new_statement = statement.execution_options(my_option=True)
An exception to this behavior is the
Connection
object, where theConnection.execution_options()
method is explicitly not generative.The kinds of options that may be passed to
Executable.execution_options()
and other related methods and parameter dictionaries include parameters that are explicitly consumed by SQLAlchemy Core or ORM, as well as arbitrary keyword arguments not defined by SQLAlchemy, which means the methods and/or parameter dictionaries may be used for user-defined parameters that interact with custom code, which may access the parameters using methods such asExecutable.get_execution_options()
andConnection.get_execution_options()
, or within selected event hooks using a dedicatedexecution_options
event parameter such asConnectionEvents.before_execute.execution_options
orORMExecuteState.execution_options
, e.g.:from sqlalchemy import event @event.listens_for(some_engine, "before_execute") def _process_opt(conn, statement, multiparams, params, execution_options): "run a SQL function before invoking a statement" if execution_options.get("do_special_thing", False): conn.exec_driver_sql("run_special_function()")
Within the scope of options that are explicitly recognized by SQLAlchemy, most apply to specific classes of objects and not others. The most common execution options include:
Connection.execution_options.isolation_level
- sets the isolation level for a connection or a class of connections via anEngine
. This option is accepted only byConnection
orEngine
.Connection.execution_options.stream_results
- indicates results should be fetched using a server side cursor; this option is accepted byConnection
, by theConnection.execute.execution_options
parameter onConnection.execute()
, and additionally byExecutable.execution_options()
on a SQL statement object, as well as by ORM constructs likeSession.execute()
.Connection.execution_options.compiled_cache
- indicates a dictionary that will serve as the SQL compilation cache for aConnection
orEngine
, as well as for ORM methods likeSession.execute()
. Can be passed asNone
to disable caching for statements. This option is not accepted byExecutable.execution_options()
as it is inadvisable to carry along a compilation cache within a statement object.Connection.execution_options.schema_translate_map
- a mapping of schema names used by the Schema Translate Map feature, accepted byConnection
,Engine
,Executable
, as well as by ORM constructs likeSession.execute()
.
See also
Connection.execution_options()
Connection.execute.execution_options
Session.execute.execution_options
ORM Execution Options - documentation on all ORM-specific execution options
-
method
sqlalchemy.sql.expression.Executable.
get_execution_options() → _ExecuteOptions¶ Get the non-SQL options which will take effect during execution.
New in version 1.3.
See also
-
method
sqlalchemy.sql.expression.Executable.
options(*options: ExecutableOption) → Self¶ Apply options to this statement.
In the general sense, options are any kind of Python object that can be interpreted by the SQL compiler for the statement. These options can be consumed by specific dialects or specific kinds of compilers.
The most commonly known kind of option are the ORM level options that apply “eager load” and other loading behaviors to an ORM query. However, options can theoretically be used for many other purposes.
For background on specific kinds of options for specific kinds of statements, refer to the documentation for those option objects.
Changed in version 1.4: - added
Executable.options()
to Core statement objects towards the goal of allowing unified Core / ORM querying capabilities.See also
Column Loading Options - refers to options specific to the usage of ORM queries
Relationship Loading with Loader Options - refers to options specific to the usage of ORM queries
-
method
- class sqlalchemy.sql.expression.Exists¶
Represent an
EXISTS
clause.See
exists()
for a description of usage.An
EXISTS
clause can also be constructed from aselect()
instance by callingSelectBase.exists()
.Members
correlate(), correlate_except(), inherit_cache, select(), select_from(), where()
Class signature
class
sqlalchemy.sql.expression.Exists
(sqlalchemy.sql.expression.UnaryExpression
)-
method
sqlalchemy.sql.expression.Exists.
correlate(*fromclauses: Literal[None, False] | _FromClauseArgument) → Self¶ Apply correlation to the subquery noted by this
Exists
.See also
-
method
sqlalchemy.sql.expression.Exists.
correlate_except(*fromclauses: Literal[None, False] | _FromClauseArgument) → Self¶ Apply correlation to the subquery noted by this
Exists
.See also
-
attribute
sqlalchemy.sql.expression.Exists.
inherit_cache: bool | None = True¶ Indicate if this
HasCacheKey
instance should make use of the cache key generation scheme used by its immediate superclass.The attribute defaults to
None
, which indicates that a construct has not yet taken into account whether or not its appropriate for it to participate in caching; this is functionally equivalent to setting the value toFalse
, except that a warning is also emitted.This flag can be set to
True
on a particular class, if the SQL that corresponds to the object does not change based on attributes which are local to this class, and not its superclass.See also
Enabling Caching Support for Custom Constructs - General guideslines for setting the
HasCacheKey.inherit_cache
attribute for third-party or user defined SQL constructs.
-
method
sqlalchemy.sql.expression.Exists.
select() → Select¶ Return a SELECT of this
Exists
.e.g.:
stmt = exists(some_table.c.id).where(some_table.c.id == 5).select()
This will produce a statement resembling:
SELECT EXISTS (SELECT id FROM some_table WHERE some_table = :param) AS anon_1
See also
select()
- general purpose method which allows for arbitrary column lists.
-
method
sqlalchemy.sql.expression.Exists.
select_from(*froms: _FromClauseArgument) → Self¶ Return a new
Exists
construct, applying the given expression to theSelect.select_from()
method of the select statement contained.Note
it is typically preferable to build a
Select
statement first, including the desired WHERE clause, then use theSelectBase.exists()
method to produce anExists
object at once.
-
method
sqlalchemy.sql.expression.Exists.
where(*clause: _ColumnExpressionArgument[bool]) → Self¶ Return a new
exists()
construct with the given expression added to its WHERE clause, joined to the existing clause via AND, if any.Note
it is typically preferable to build a
Select
statement first, including the desired WHERE clause, then use theSelectBase.exists()
method to produce anExists
object at once.
-
method
- class sqlalchemy.sql.expression.FromClause¶
Represent an element that can be used within the
FROM
clause of aSELECT
statement.The most common forms of
FromClause
are theTable
and theselect()
constructs. Key features common to allFromClause
objects include:a
c
collection, which provides per-name access to a collection ofColumnElement
objects.a
primary_key
attribute, which is a collection of all thoseColumnElement
objects that indicate theprimary_key
flag.Methods to generate various derivations of a “from” clause, including
FromClause.alias()
,FromClause.join()
,FromClause.select()
.
Members
alias(), c, columns, description, entity_namespace, exported_columns, foreign_keys, is_derived_from(), join(), outerjoin(), primary_key, schema, select(), tablesample()
Class signature
class
sqlalchemy.sql.expression.FromClause
(sqlalchemy.sql.roles.AnonymizedFromClauseRole
,sqlalchemy.sql.expression.Selectable
)-
method
sqlalchemy.sql.expression.FromClause.
alias(name: str | None = None, flat: bool = False) → NamedFromClause¶ Return an alias of this
FromClause
.E.g.:
a2 = some_table.alias("a2")
The above code creates an
Alias
object which can be used as a FROM clause in any SELECT statement.
-
attribute
sqlalchemy.sql.expression.FromClause.
c¶ A synonym for
FromClause.columns
- Returns:
-
attribute
sqlalchemy.sql.expression.FromClause.
columns¶ A named-based collection of
ColumnElement
objects maintained by thisFromClause
.The
columns
, orc
collection, is the gateway to the construction of SQL expressions using table-bound or other selectable-bound columns:select(mytable).where(mytable.c.somecolumn == 5)
- Returns:
a
ColumnCollection
object.
-
attribute
sqlalchemy.sql.expression.FromClause.
description¶ A brief description of this
FromClause
.Used primarily for error message formatting.
-
attribute
sqlalchemy.sql.expression.FromClause.
entity_namespace¶ Return a namespace used for name-based access in SQL expressions.
This is the namespace that is used to resolve “filter_by()” type expressions, such as:
stmt.filter_by(address="some address")
It defaults to the
.c
collection, however internally it can be overridden using the “entity_namespace” annotation to deliver alternative results.
-
attribute
sqlalchemy.sql.expression.FromClause.
exported_columns¶ A
ColumnCollection
that represents the “exported” columns of thisSelectable
.The “exported” columns for a
FromClause
object are synonymous with theFromClause.columns
collection.New in version 1.4.
-
attribute
sqlalchemy.sql.expression.FromClause.
foreign_keys¶ Return the collection of
ForeignKey
marker objects which this FromClause references.Each
ForeignKey
is a member of aTable
-wideForeignKeyConstraint
.See also
-
method
sqlalchemy.sql.expression.FromClause.
is_derived_from(fromclause: FromClause | None) → bool¶ Return
True
if thisFromClause
is ‘derived’ from the givenFromClause
.An example would be an Alias of a Table is derived from that Table.
-
method
sqlalchemy.sql.expression.FromClause.
join(right: _FromClauseArgument, onclause: _ColumnExpressionArgument[bool] | None = None, isouter: bool = False, full: bool = False) → Join¶ Return a
Join
from thisFromClause
to anotherFromClause
.E.g.:
from sqlalchemy import join j = user_table.join( address_table, user_table.c.id == address_table.c.user_id ) stmt = select(user_table).select_from(j)
would emit SQL along the lines of:
SELECT user.id, user.name FROM user JOIN address ON user.id = address.user_id
- Parameters:
right¶ – the right side of the join; this is any
FromClause
object such as aTable
object, and may also be a selectable-compatible object such as an ORM-mapped class.onclause¶ – a SQL expression representing the ON clause of the join. If left at
None
,FromClause.join()
will attempt to join the two tables based on a foreign key relationship.isouter¶ – if True, render a LEFT OUTER JOIN, instead of JOIN.
full¶ – if True, render a FULL OUTER JOIN, instead of LEFT OUTER JOIN. Implies
FromClause.join.isouter
.
-
method
sqlalchemy.sql.expression.FromClause.
outerjoin(right: _FromClauseArgument, onclause: _ColumnExpressionArgument[bool] | None = None, full: bool = False) → Join¶ Return a
Join
from thisFromClause
to anotherFromClause
, with the “isouter” flag set to True.E.g.:
from sqlalchemy import outerjoin j = user_table.outerjoin( address_table, user_table.c.id == address_table.c.user_id )
The above is equivalent to:
j = user_table.join( address_table, user_table.c.id == address_table.c.user_id, isouter=True )
- Parameters:
right¶ – the right side of the join; this is any
FromClause
object such as aTable
object, and may also be a selectable-compatible object such as an ORM-mapped class.onclause¶ – a SQL expression representing the ON clause of the join. If left at
None
,FromClause.join()
will attempt to join the two tables based on a foreign key relationship.full¶ – if True, render a FULL OUTER JOIN, instead of LEFT OUTER JOIN.
-
attribute
sqlalchemy.sql.expression.FromClause.
primary_key¶ Return the iterable collection of
Column
objects which comprise the primary key of this_selectable.FromClause
.For a
Table
object, this collection is represented by thePrimaryKeyConstraint
which itself is an iterable collection ofColumn
objects.
-
attribute
sqlalchemy.sql.expression.FromClause.
schema: str | None = None¶ Define the ‘schema’ attribute for this
FromClause
.This is typically
None
for most objects except that ofTable
, where it is taken as the value of theTable.schema
argument.
-
method
sqlalchemy.sql.expression.FromClause.
select() → Select¶ Return a SELECT of this
FromClause
.e.g.:
stmt = some_table.select().where(some_table.c.id == 5)
See also
select()
- general purpose method which allows for arbitrary column lists.
-
method
sqlalchemy.sql.expression.FromClause.
tablesample(sampling: float | Function[Any], name: str | None = None, seed: roles.ExpressionElementRole[Any] | None = None) → TableSample¶ Return a TABLESAMPLE alias of this
FromClause
.The return value is the
TableSample
construct also provided by the top-leveltablesample()
function.See also
tablesample()
- usage guidelines and parameters
- class sqlalchemy.sql.expression.GenerativeSelect¶
Base class for SELECT statements where additional elements can be added.
This serves as the base for
Select
andCompoundSelect
where elements such as ORDER BY, GROUP BY can be added and column rendering can be controlled. Compare toTextualSelect
, which, while it subclassesSelectBase
and is also a SELECT construct, represents a fixed textual string which cannot be altered at this level, only wrapped as a subquery.Members
fetch(), get_label_style(), group_by(), limit(), offset(), order_by(), set_label_style(), slice(), with_for_update()
Class signature
class
sqlalchemy.sql.expression.GenerativeSelect
(sqlalchemy.sql.expression.SelectBase
,sqlalchemy.sql.expression.Generative
)-
method
sqlalchemy.sql.expression.GenerativeSelect.
fetch(count: _LimitOffsetType, with_ties: bool = False, percent: bool = False) → Self¶ Return a new selectable with the given FETCH FIRST criterion applied.
This is a numeric value which usually renders as
FETCH {FIRST | NEXT} [ count ] {ROW | ROWS} {ONLY | WITH TIES}
expression in the resulting select. This functionality is is currently implemented for Oracle Database, PostgreSQL, MSSQL.Use
GenerativeSelect.offset()
to specify the offset.Note
The
GenerativeSelect.fetch()
method will replace any clause applied withGenerativeSelect.limit()
.New in version 1.4.
- Parameters:
count¶ – an integer COUNT parameter, or a SQL expression that provides an integer result. When
percent=True
this will represent the percentage of rows to return, not the absolute value. PassNone
to reset it.with_ties¶ – When
True
, the WITH TIES option is used to return any additional rows that tie for the last place in the result set according to theORDER BY
clause. TheORDER BY
may be mandatory in this case. Defaults toFalse
percent¶ – When
True
,count
represents the percentage of the total number of selected rows to return. Defaults toFalse
-
method
sqlalchemy.sql.expression.GenerativeSelect.
get_label_style() → SelectLabelStyle¶ Retrieve the current label style.
New in version 1.4.
-
method
sqlalchemy.sql.expression.GenerativeSelect.
group_by(_GenerativeSelect__first: Literal[None, _NoArg.NO_ARG] | _ColumnExpressionOrStrLabelArgument[Any] = _NoArg.NO_ARG, *clauses: _ColumnExpressionOrStrLabelArgument[Any]) → Self¶ Return a new selectable with the given list of GROUP BY criterion applied.
All existing GROUP BY settings can be suppressed by passing
None
.e.g.:
stmt = select(table.c.name, func.max(table.c.stat)).group_by(table.c.name)
- Parameters:
*clauses¶ – a series of
ColumnElement
constructs which will be used to generate an GROUP BY clause.
-
method
sqlalchemy.sql.expression.GenerativeSelect.
limit(limit: _LimitOffsetType) → Self¶ Return a new selectable with the given LIMIT criterion applied.
This is a numerical value which usually renders as a
LIMIT
expression in the resulting select. Backends that don’t supportLIMIT
will attempt to provide similar functionality.Note
The
GenerativeSelect.limit()
method will replace any clause applied withGenerativeSelect.fetch()
.- Parameters:
limit¶ – an integer LIMIT parameter, or a SQL expression that provides an integer result. Pass
None
to reset it.
-
method
sqlalchemy.sql.expression.GenerativeSelect.
offset(offset: _LimitOffsetType) → Self¶ Return a new selectable with the given OFFSET criterion applied.
This is a numeric value which usually renders as an
OFFSET
expression in the resulting select. Backends that don’t supportOFFSET
will attempt to provide similar functionality.- Parameters:
offset¶ – an integer OFFSET parameter, or a SQL expression that provides an integer result. Pass
None
to reset it.
-
method
sqlalchemy.sql.expression.GenerativeSelect.
order_by(_GenerativeSelect__first: Literal[None, _NoArg.NO_ARG] | _ColumnExpressionOrStrLabelArgument[Any] = _NoArg.NO_ARG, *clauses: _ColumnExpressionOrStrLabelArgument[Any]) → Self¶ Return a new selectable with the given list of ORDER BY criteria applied.
e.g.:
stmt = select(table).order_by(table.c.id, table.c.name)
Calling this method multiple times is equivalent to calling it once with all the clauses concatenated. All existing ORDER BY criteria may be cancelled by passing
None
by itself. New ORDER BY criteria may then be added by invokingQuery.order_by()
again, e.g.:# will erase all ORDER BY and ORDER BY new_col alone stmt = stmt.order_by(None).order_by(new_col)
- Parameters:
*clauses¶ – a series of
ColumnElement
constructs which will be used to generate an ORDER BY clause.
See also
ORDER BY - in the SQLAlchemy Unified Tutorial
Ordering or Grouping by a Label - in the SQLAlchemy Unified Tutorial
-
method
sqlalchemy.sql.expression.GenerativeSelect.
set_label_style(style: SelectLabelStyle) → Self¶ Return a new selectable with the specified label style.
There are three “label styles” available,
SelectLabelStyle.LABEL_STYLE_DISAMBIGUATE_ONLY
,SelectLabelStyle.LABEL_STYLE_TABLENAME_PLUS_COL
, andSelectLabelStyle.LABEL_STYLE_NONE
. The default style isSelectLabelStyle.LABEL_STYLE_DISAMBIGUATE_ONLY
.In modern SQLAlchemy, there is not generally a need to change the labeling style, as per-expression labels are more effectively used by making use of the
ColumnElement.label()
method. In past versions,LABEL_STYLE_TABLENAME_PLUS_COL
was used to disambiguate same-named columns from different tables, aliases, or subqueries; the newerLABEL_STYLE_DISAMBIGUATE_ONLY
now applies labels only to names that conflict with an existing name so that the impact of this labeling is minimal.The rationale for disambiguation is mostly so that all column expressions are available from a given
FromClause.c
collection when a subquery is created.New in version 1.4: - the
GenerativeSelect.set_label_style()
method replaces the previous combination of.apply_labels()
,.with_labels()
anduse_labels=True
methods and/or parameters.See also
LABEL_STYLE_DISAMBIGUATE_ONLY
LABEL_STYLE_TABLENAME_PLUS_COL
LABEL_STYLE_NONE
LABEL_STYLE_DEFAULT
-
method
sqlalchemy.sql.expression.GenerativeSelect.
slice(start: int, stop: int) → Self¶ Apply LIMIT / OFFSET to this statement based on a slice.
The start and stop indices behave like the argument to Python’s built-in
range()
function. This method provides an alternative to usingLIMIT
/OFFSET
to get a slice of the query.For example,
stmt = select(User).order_by(User.id).slice(1, 3)
renders as
SELECT users.id AS users_id, users.name AS users_name FROM users ORDER BY users.id LIMIT ? OFFSET ? (2, 1)
Note
The
GenerativeSelect.slice()
method will replace any clause applied withGenerativeSelect.fetch()
.New in version 1.4: Added the
GenerativeSelect.slice()
method generalized from the ORM.
-
method
sqlalchemy.sql.expression.GenerativeSelect.
with_for_update(*, nowait: bool = False, read: bool = False, of: _ForUpdateOfArgument | None = None, skip_locked: bool = False, key_share: bool = False) → Self¶ Specify a
FOR UPDATE
clause for thisGenerativeSelect
.E.g.:
stmt = select(table).with_for_update(nowait=True)
On a database like PostgreSQL or Oracle Database, the above would render a statement like:
SELECT table.a, table.b FROM table FOR UPDATE NOWAIT
on other backends, the
nowait
option is ignored and instead would produce:SELECT table.a, table.b FROM table FOR UPDATE
When called with no arguments, the statement will render with the suffix
FOR UPDATE
. Additional arguments can then be provided which allow for common database-specific variants.- Parameters:
nowait¶ – boolean; will render
FOR UPDATE NOWAIT
on Oracle Database and PostgreSQL dialects.read¶ – boolean; will render
LOCK IN SHARE MODE
on MySQL,FOR SHARE
on PostgreSQL. On PostgreSQL, when combined withnowait
, will renderFOR SHARE NOWAIT
.of¶ – SQL expression or list of SQL expression elements, (typically
Column
objects or a compatible expression, for some backends may also be a table expression) which will render into aFOR UPDATE OF
clause; supported by PostgreSQL, Oracle Database, some MySQL versions and possibly others. May render as a table or as a column depending on backend.skip_locked¶ – boolean, will render
FOR UPDATE SKIP LOCKED
on Oracle Database and PostgreSQL dialects orFOR SHARE SKIP LOCKED
ifread=True
is also specified.key_share¶ – boolean, will render
FOR NO KEY UPDATE
, or if combined withread=True
will renderFOR KEY SHARE
, on the PostgreSQL dialect.
-
method
- class sqlalchemy.sql.expression.HasCTE¶
Mixin that declares a class to include CTE support.
Class signature
class
sqlalchemy.sql.expression.HasCTE
(sqlalchemy.sql.roles.HasCTERole
,sqlalchemy.sql.expression.SelectsRows
)-
method
sqlalchemy.sql.expression.HasCTE.
add_cte(*ctes: CTE, nest_here: bool = False) → Self¶ Add one or more
CTE
constructs to this statement.This method will associate the given
CTE
constructs with the parent statement such that they will each be unconditionally rendered in the WITH clause of the final statement, even if not referenced elsewhere within the statement or any sub-selects.The optional
HasCTE.add_cte.nest_here
parameter when set to True will have the effect that each givenCTE
will render in a WITH clause rendered directly along with this statement, rather than being moved to the top of the ultimate rendered statement, even if this statement is rendered as a subquery within a larger statement.This method has two general uses. One is to embed CTE statements that serve some purpose without being referenced explicitly, such as the use case of embedding a DML statement such as an INSERT or UPDATE as a CTE inline with a primary statement that may draw from its results indirectly. The other is to provide control over the exact placement of a particular series of CTE constructs that should remain rendered directly in terms of a particular statement that may be nested in a larger statement.
E.g.:
from sqlalchemy import table, column, select t = table("t", column("c1"), column("c2")) ins = t.insert().values({"c1": "x", "c2": "y"}).cte() stmt = select(t).add_cte(ins)
Would render:
WITH anon_1 AS ( INSERT INTO t (c1, c2) VALUES (:param_1, :param_2) ) SELECT t.c1, t.c2 FROM t
Above, the “anon_1” CTE is not referenced in the SELECT statement, however still accomplishes the task of running an INSERT statement.
Similarly in a DML-related context, using the PostgreSQL
Insert
construct to generate an “upsert”:from sqlalchemy import table, column from sqlalchemy.dialects.postgresql import insert t = table("t", column("c1"), column("c2")) delete_statement_cte = t.delete().where(t.c.c1 < 1).cte("deletions") insert_stmt = insert(t).values({"c1": 1, "c2": 2}) update_statement = insert_stmt.on_conflict_do_update( index_elements=[t.c.c1], set_={ "c1": insert_stmt.excluded.c1, "c2": insert_stmt.excluded.c2, }, ).add_cte(delete_statement_cte) print(update_statement)
The above statement renders as:
WITH deletions AS ( DELETE FROM t WHERE t.c1 < %(c1_1)s ) INSERT INTO t (c1, c2) VALUES (%(c1)s, %(c2)s) ON CONFLICT (c1) DO UPDATE SET c1 = excluded.c1, c2 = excluded.c2
New in version 1.4.21.
- Parameters:
*ctes¶ –
zero or more
CTE
constructs.Changed in version 2.0: Multiple CTE instances are accepted
nest_here¶ –
if True, the given CTE or CTEs will be rendered as though they specified the
HasCTE.cte.nesting
flag toTrue
when they were added to thisHasCTE
. Assuming the given CTEs are not referenced in an outer-enclosing statement as well, the CTEs given should render at the level of this statement when this flag is given.New in version 2.0.
See also
-
method
sqlalchemy.sql.expression.HasCTE.
cte(name: str | None = None, recursive: bool = False, nesting: bool = False) → CTE¶ Return a new
CTE
, or Common Table Expression instance.Common table expressions are a SQL standard whereby SELECT statements can draw upon secondary statements specified along with the primary statement, using a clause called “WITH”. Special semantics regarding UNION can also be employed to allow “recursive” queries, where a SELECT statement can draw upon the set of rows that have previously been selected.
CTEs can also be applied to DML constructs UPDATE, INSERT and DELETE on some databases, both as a source of CTE rows when combined with RETURNING, as well as a consumer of CTE rows.
SQLAlchemy detects
CTE
objects, which are treated similarly toAlias
objects, as special elements to be delivered to the FROM clause of the statement as well as to a WITH clause at the top of the statement.For special prefixes such as PostgreSQL “MATERIALIZED” and “NOT MATERIALIZED”, the
CTE.prefix_with()
method may be used to establish these.Changed in version 1.3.13: Added support for prefixes. In particular - MATERIALIZED and NOT MATERIALIZED.
- Parameters:
name¶ – name given to the common table expression. Like
FromClause.alias()
, the name can be left asNone
in which case an anonymous symbol will be used at query compile time.recursive¶ – if
True
, will renderWITH RECURSIVE
. A recursive common table expression is intended to be used in conjunction with UNION ALL in order to derive rows from those already selected.nesting¶ –
if
True
, will render the CTE locally to the statement in which it is referenced. For more complex scenarios, theHasCTE.add_cte()
method using theHasCTE.add_cte.nest_here
parameter may also be used to more carefully control the exact placement of a particular CTE.New in version 1.4.24.
See also
The following examples include two from PostgreSQL’s documentation at https://www.postgresql.org/docs/current/static/queries-with.html, as well as additional examples.
Example 1, non recursive:
from sqlalchemy import ( Table, Column, String, Integer, MetaData, select, func, ) metadata = MetaData() orders = Table( "orders", metadata, Column("region", String), Column("amount", Integer), Column("product", String), Column("quantity", Integer), ) regional_sales = ( select(orders.c.region, func.sum(orders.c.amount).label("total_sales")) .group_by(orders.c.region) .cte("regional_sales") ) top_regions = ( select(regional_sales.c.region) .where( regional_sales.c.total_sales > select(func.sum(regional_sales.c.total_sales) / 10) ) .cte("top_regions") ) statement = ( select( orders.c.region, orders.c.product, func.sum(orders.c.quantity).label("product_units"), func.sum(orders.c.amount).label("product_sales"), ) .where(orders.c.region.in_(select(top_regions.c.region))) .group_by(orders.c.region, orders.c.product) ) result = conn.execute(statement).fetchall()
Example 2, WITH RECURSIVE:
from sqlalchemy import ( Table, Column, String, Integer, MetaData, select, func, ) metadata = MetaData() parts = Table( "parts", metadata, Column("part", String), Column("sub_part", String), Column("quantity", Integer), ) included_parts = ( select(parts.c.sub_part, parts.c.part, parts.c.quantity) .where(parts.c.part == "our part") .cte(recursive=True) ) incl_alias = included_parts.alias() parts_alias = parts.alias() included_parts = included_parts.union_all( select( parts_alias.c.sub_part, parts_alias.c.part, parts_alias.c.quantity ).where(parts_alias.c.part == incl_alias.c.sub_part) ) statement = select( included_parts.c.sub_part, func.sum(included_parts.c.quantity).label("total_quantity"), ).group_by(included_parts.c.sub_part) result = conn.execute(statement).fetchall()
Example 3, an upsert using UPDATE and INSERT with CTEs:
from datetime import date from sqlalchemy import ( MetaData, Table, Column, Integer, Date, select, literal, and_, exists, ) metadata = MetaData() visitors = Table( "visitors", metadata, Column("product_id", Integer, primary_key=True), Column("date", Date, primary_key=True), Column("count", Integer), ) # add 5 visitors for the product_id == 1 product_id = 1 day = date.today() count = 5 update_cte = ( visitors.update() .where( and_(visitors.c.product_id == product_id, visitors.c.date == day) ) .values(count=visitors.c.count + count) .returning(literal(1)) .cte("update_cte") ) upsert = visitors.insert().from_select( [visitors.c.product_id, visitors.c.date, visitors.c.count], select(literal(product_id), literal(day), literal(count)).where( ~exists(update_cte.select()) ), ) connection.execute(upsert)
Example 4, Nesting CTE (SQLAlchemy 1.4.24 and above):
value_a = select(literal("root").label("n")).cte("value_a") # A nested CTE with the same name as the root one value_a_nested = select(literal("nesting").label("n")).cte( "value_a", nesting=True ) # Nesting CTEs takes ascendency locally # over the CTEs at a higher level value_b = select(value_a_nested.c.n).cte("value_b") value_ab = select(value_a.c.n.label("a"), value_b.c.n.label("b"))
The above query will render the second CTE nested inside the first, shown with inline parameters below as:
WITH value_a AS (SELECT 'root' AS n), value_b AS (WITH value_a AS (SELECT 'nesting' AS n) SELECT value_a.n AS n FROM value_a) SELECT value_a.n AS a, value_b.n AS b FROM value_a, value_b
The same CTE can be set up using the
HasCTE.add_cte()
method as follows (SQLAlchemy 2.0 and above):value_a = select(literal("root").label("n")).cte("value_a") # A nested CTE with the same name as the root one value_a_nested = select(literal("nesting").label("n")).cte("value_a") # Nesting CTEs takes ascendency locally # over the CTEs at a higher level value_b = ( select(value_a_nested.c.n) .add_cte(value_a_nested, nest_here=True) .cte("value_b") ) value_ab = select(value_a.c.n.label("a"), value_b.c.n.label("b"))
Example 5, Non-Linear CTE (SQLAlchemy 1.4.28 and above):
edge = Table( "edge", metadata, Column("id", Integer, primary_key=True), Column("left", Integer), Column("right", Integer), ) root_node = select(literal(1).label("node")).cte("nodes", recursive=True) left_edge = select(edge.c.left).join( root_node, edge.c.right == root_node.c.node ) right_edge = select(edge.c.right).join( root_node, edge.c.left == root_node.c.node ) subgraph_cte = root_node.union(left_edge, right_edge) subgraph = select(subgraph_cte)
The above query will render 2 UNIONs inside the recursive CTE:
WITH RECURSIVE nodes(node) AS ( SELECT 1 AS node UNION SELECT edge."left" AS "left" FROM edge JOIN nodes ON edge."right" = nodes.node UNION SELECT edge."right" AS "right" FROM edge JOIN nodes ON edge."left" = nodes.node ) SELECT nodes.node FROM nodes
See also
Query.cte()
- ORM version ofHasCTE.cte()
.
-
method
- class sqlalchemy.sql.expression.HasPrefixes¶
Members
-
method
sqlalchemy.sql.expression.HasPrefixes.
prefix_with(*prefixes: _TextCoercedExpressionArgument[Any], dialect: str = '*') → Self¶ Add one or more expressions following the statement keyword, i.e. SELECT, INSERT, UPDATE, or DELETE. Generative.
This is used to support backend-specific prefix keywords such as those provided by MySQL.
E.g.:
stmt = table.insert().prefix_with("LOW_PRIORITY", dialect="mysql") # MySQL 5.7 optimizer hints stmt = select(table).prefix_with("/*+ BKA(t1) */", dialect="mysql")
Multiple prefixes can be specified by multiple calls to
HasPrefixes.prefix_with()
.- Parameters:
*prefixes¶ – textual or
ClauseElement
construct which will be rendered following the INSERT, UPDATE, or DELETE keyword.dialect¶ – optional string dialect name which will limit rendering of this prefix to only that dialect.
-
method
- class sqlalchemy.sql.expression.HasSuffixes¶
Members
-
method
sqlalchemy.sql.expression.HasSuffixes.
suffix_with(*suffixes: _TextCoercedExpressionArgument[Any], dialect: str = '*') → Self¶ Add one or more expressions following the statement as a whole.
This is used to support backend-specific suffix keywords on certain constructs.
E.g.:
stmt = ( select(col1, col2) .cte() .suffix_with( "cycle empno set y_cycle to 1 default 0", dialect="oracle" ) )
Multiple suffixes can be specified by multiple calls to
HasSuffixes.suffix_with()
.- Parameters:
*suffixes¶ – textual or
ClauseElement
construct which will be rendered following the target clause.dialect¶ – Optional string dialect name which will limit rendering of this suffix to only that dialect.
-
method
- class sqlalchemy.sql.expression.Join¶
Represent a
JOIN
construct between twoFromClause
elements.The public constructor function for
Join
is the module-leveljoin()
function, as well as theFromClause.join()
method of anyFromClause
(e.g. such asTable
).Members
__init__(), description, is_derived_from(), select(), self_group()
Class signature
class
sqlalchemy.sql.expression.Join
(sqlalchemy.sql.roles.DMLTableRole
,sqlalchemy.sql.expression.FromClause
)-
method
sqlalchemy.sql.expression.Join.
__init__(left: _FromClauseArgument, right: _FromClauseArgument, onclause: _OnClauseArgument | None = None, isouter: bool = False, full: bool = False)¶ Construct a new
Join
.The usual entrypoint here is the
join()
function or theFromClause.join()
method of anyFromClause
object.
-
attribute
sqlalchemy.sql.expression.Join.
description¶
-
method
sqlalchemy.sql.expression.Join.
is_derived_from(fromclause: FromClause | None) → bool¶ Return
True
if thisFromClause
is ‘derived’ from the givenFromClause
.An example would be an Alias of a Table is derived from that Table.
-
method
sqlalchemy.sql.expression.Join.
select() → Select¶ Create a
Select
from thisJoin
.E.g.:
stmt = table_a.join(table_b, table_a.c.id == table_b.c.a_id) stmt = stmt.select()
The above will produce a SQL string resembling:
SELECT table_a.id, table_a.col, table_b.id, table_b.a_id FROM table_a JOIN table_b ON table_a.id = table_b.a_id
-
method
sqlalchemy.sql.expression.Join.
self_group(against: OperatorType | None = None) → FromGrouping¶ Apply a ‘grouping’ to this
ClauseElement
.This method is overridden by subclasses to return a “grouping” construct, i.e. parenthesis. In particular it’s used by “binary” expressions to provide a grouping around themselves when placed into a larger expression, as well as by
select()
constructs when placed into the FROM clause of anotherselect()
. (Note that subqueries should be normally created using theSelect.alias()
method, as many platforms require nested SELECT statements to be named).As expressions are composed together, the application of
self_group()
is automatic - end-user code should never need to use this method directly. Note that SQLAlchemy’s clause constructs take operator precedence into account - so parenthesis might not be needed, for example, in an expression likex OR (y AND z)
- AND takes precedence over OR.The base
self_group()
method ofClauseElement
just returns self.
-
method
- class sqlalchemy.sql.expression.Lateral¶
Represent a LATERAL subquery.
This object is constructed from the
lateral()
module level function as well as theFromClause.lateral()
method available on allFromClause
subclasses.While LATERAL is part of the SQL standard, currently only more recent PostgreSQL versions provide support for this keyword.
See also
LATERAL correlation - overview of usage.
Members
Class signature
class
sqlalchemy.sql.expression.Lateral
(sqlalchemy.sql.expression.FromClauseAlias
,sqlalchemy.sql.expression.LateralFromClause
)-
attribute
sqlalchemy.sql.expression.Lateral.
inherit_cache: bool | None = True¶ Indicate if this
HasCacheKey
instance should make use of the cache key generation scheme used by its immediate superclass.The attribute defaults to
None
, which indicates that a construct has not yet taken into account whether or not its appropriate for it to participate in caching; this is functionally equivalent to setting the value toFalse
, except that a warning is also emitted.This flag can be set to
True
on a particular class, if the SQL that corresponds to the object does not change based on attributes which are local to this class, and not its superclass.See also
Enabling Caching Support for Custom Constructs - General guideslines for setting the
HasCacheKey.inherit_cache
attribute for third-party or user defined SQL constructs.
-
attribute
- class sqlalchemy.sql.expression.ReturnsRows¶
The base-most class for Core constructs that have some concept of columns that can represent rows.
While the SELECT statement and TABLE are the primary things we think of in this category, DML like INSERT, UPDATE and DELETE can also specify RETURNING which means they can be used in CTEs and other forms, and PostgreSQL has functions that return rows also.
New in version 1.4.
Members
Class signature
class
sqlalchemy.sql.expression.ReturnsRows
(sqlalchemy.sql.roles.ReturnsRowsRole
,sqlalchemy.sql.expression.DQLDMLClauseElement
)-
attribute
sqlalchemy.sql.expression.ReturnsRows.
exported_columns¶ A
ColumnCollection
that represents the “exported” columns of thisReturnsRows
.The “exported” columns represent the collection of
ColumnElement
expressions that are rendered by this SQL construct. There are primary varieties which are the “FROM clause columns” of a FROM clause, such as a table, join, or subquery, the “SELECTed columns”, which are the columns in the “columns clause” of a SELECT statement, and the RETURNING columns in a DML statement..New in version 1.4.
-
method
sqlalchemy.sql.expression.ReturnsRows.
is_derived_from(fromclause: FromClause | None) → bool¶ Return
True
if thisReturnsRows
is ‘derived’ from the givenFromClause
.An example would be an Alias of a Table is derived from that Table.
-
attribute
- class sqlalchemy.sql.expression.ScalarSelect¶
Represent a scalar subquery.
A
ScalarSelect
is created by invoking theSelectBase.scalar_subquery()
method. The object then participates in other SQL expressions as a SQL column expression within theColumnElement
hierarchy.Members
correlate(), correlate_except(), inherit_cache, self_group(), where()
Class signature
class
sqlalchemy.sql.expression.ScalarSelect
(sqlalchemy.sql.roles.InElementRole
,sqlalchemy.sql.expression.Generative
,sqlalchemy.sql.expression.GroupedElement
,sqlalchemy.sql.expression.ColumnElement
)-
method
sqlalchemy.sql.expression.ScalarSelect.
correlate(*fromclauses: Literal[None, False] | _FromClauseArgument) → Self¶ Return a new
ScalarSelect
which will correlate the given FROM clauses to that of an enclosingSelect
.This method is mirrored from the
Select.correlate()
method of the underlyingSelect
. The method applies the :meth:_sql.Select.correlate` method, then returns a newScalarSelect
against that statement.New in version 1.4: Previously, the
ScalarSelect.correlate()
method was only available fromSelect
.- Parameters:
*fromclauses¶ – a list of one or more
FromClause
constructs, or other compatible constructs (i.e. ORM-mapped classes) to become part of the correlate collection.
-
method
sqlalchemy.sql.expression.ScalarSelect.
correlate_except(*fromclauses: Literal[None, False] | _FromClauseArgument) → Self¶ Return a new
ScalarSelect
which will omit the given FROM clauses from the auto-correlation process.This method is mirrored from the
Select.correlate_except()
method of the underlyingSelect
. The method applies the :meth:_sql.Select.correlate_except` method, then returns a newScalarSelect
against that statement.New in version 1.4: Previously, the
ScalarSelect.correlate_except()
method was only available fromSelect
.- Parameters:
*fromclauses¶ – a list of one or more
FromClause
constructs, or other compatible constructs (i.e. ORM-mapped classes) to become part of the correlate-exception collection.
-
attribute
sqlalchemy.sql.expression.ScalarSelect.
inherit_cache: bool | None = True¶ Indicate if this
HasCacheKey
instance should make use of the cache key generation scheme used by its immediate superclass.The attribute defaults to
None
, which indicates that a construct has not yet taken into account whether or not its appropriate for it to participate in caching; this is functionally equivalent to setting the value toFalse
, except that a warning is also emitted.This flag can be set to
True
on a particular class, if the SQL that corresponds to the object does not change based on attributes which are local to this class, and not its superclass.See also
Enabling Caching Support for Custom Constructs - General guideslines for setting the
HasCacheKey.inherit_cache
attribute for third-party or user defined SQL constructs.
-
method
sqlalchemy.sql.expression.ScalarSelect.
self_group(against: OperatorType | None = None) → Self¶ Apply a ‘grouping’ to this
ClauseElement
.This method is overridden by subclasses to return a “grouping” construct, i.e. parenthesis. In particular it’s used by “binary” expressions to provide a grouping around themselves when placed into a larger expression, as well as by
select()
constructs when placed into the FROM clause of anotherselect()
. (Note that subqueries should be normally created using theSelect.alias()
method, as many platforms require nested SELECT statements to be named).As expressions are composed together, the application of
self_group()
is automatic - end-user code should never need to use this method directly. Note that SQLAlchemy’s clause constructs take operator precedence into account - so parenthesis might not be needed, for example, in an expression likex OR (y AND z)
- AND takes precedence over OR.The base
self_group()
method ofClauseElement
just returns self.
-
method
sqlalchemy.sql.expression.ScalarSelect.
where(crit: _ColumnExpressionArgument[bool]) → Self¶ Apply a WHERE clause to the SELECT statement referred to by this
ScalarSelect
.
-
method
- class sqlalchemy.sql.expression.Select¶
Represents a
SELECT
statement.The
Select
object is normally constructed using theselect()
function. See that function for details.Members
__init__(), add_columns(), add_cte(), alias(), as_scalar(), c, column(), column_descriptions, columns_clause_froms, correlate(), correlate_except(), corresponding_column(), cte(), distinct(), except_(), except_all(), execution_options(), exists(), exported_columns, fetch(), filter(), filter_by(), from_statement(), froms, get_children(), get_execution_options(), get_final_froms(), get_label_style(), group_by(), having(), inherit_cache, inner_columns, intersect(), intersect_all(), is_derived_from(), join(), join_from(), label(), lateral(), limit(), offset(), options(), order_by(), outerjoin(), outerjoin_from(), prefix_with(), reduce_columns(), replace_selectable(), scalar_subquery(), select(), select_from(), selected_columns, self_group(), set_label_style(), slice(), subquery(), suffix_with(), union(), union_all(), where(), whereclause, with_for_update(), with_hint(), with_only_columns(), with_statement_hint()
Class signature
class
sqlalchemy.sql.expression.Select
(sqlalchemy.sql.expression.HasPrefixes
,sqlalchemy.sql.expression.HasSuffixes
,sqlalchemy.sql.expression.HasHints
,sqlalchemy.sql.expression.HasCompileState
,sqlalchemy.sql.expression._SelectFromElements
,sqlalchemy.sql.expression.GenerativeSelect
,sqlalchemy.sql.expression.TypedReturnsRows
)-
method
sqlalchemy.sql.expression.Select.
__init__(*entities: _ColumnsClauseArgument[Any])¶ Construct a new
Select
.
-
method
sqlalchemy.sql.expression.Select.
add_columns(*entities: _ColumnsClauseArgument[Any]) → Select[Any]¶ Return a new
select()
construct with the given entities appended to its columns clause.E.g.:
my_select = my_select.add_columns(table.c.new_column)
The original expressions in the columns clause remain in place. To replace the original expressions with new ones, see the method
Select.with_only_columns()
.- Parameters:
*entities¶ – column, table, or other entity expressions to be added to the columns clause
See also
Select.with_only_columns()
- replaces existing expressions rather than appending.Selecting Multiple ORM Entities Simultaneously - ORM-centric example
-
method
sqlalchemy.sql.expression.Select.
add_cte(*ctes: CTE, nest_here: bool = False) → Self¶ inherited from the
HasCTE.add_cte()
method ofHasCTE
Add one or more
CTE
constructs to this statement.This method will associate the given
CTE
constructs with the parent statement such that they will each be unconditionally rendered in the WITH clause of the final statement, even if not referenced elsewhere within the statement or any sub-selects.The optional
HasCTE.add_cte.nest_here
parameter when set to True will have the effect that each givenCTE
will render in a WITH clause rendered directly along with this statement, rather than being moved to the top of the ultimate rendered statement, even if this statement is rendered as a subquery within a larger statement.This method has two general uses. One is to embed CTE statements that serve some purpose without being referenced explicitly, such as the use case of embedding a DML statement such as an INSERT or UPDATE as a CTE inline with a primary statement that may draw from its results indirectly. The other is to provide control over the exact placement of a particular series of CTE constructs that should remain rendered directly in terms of a particular statement that may be nested in a larger statement.
E.g.:
from sqlalchemy import table, column, select t = table("t", column("c1"), column("c2")) ins = t.insert().values({"c1": "x", "c2": "y"}).cte() stmt = select(t).add_cte(ins)
Would render:
WITH anon_1 AS ( INSERT INTO t (c1, c2) VALUES (:param_1, :param_2) ) SELECT t.c1, t.c2 FROM t
Above, the “anon_1” CTE is not referenced in the SELECT statement, however still accomplishes the task of running an INSERT statement.
Similarly in a DML-related context, using the PostgreSQL
Insert
construct to generate an “upsert”:from sqlalchemy import table, column from sqlalchemy.dialects.postgresql import insert t = table("t", column("c1"), column("c2")) delete_statement_cte = t.delete().where(t.c.c1 < 1).cte("deletions") insert_stmt = insert(t).values({"c1": 1, "c2": 2}) update_statement = insert_stmt.on_conflict_do_update( index_elements=[t.c.c1], set_={ "c1": insert_stmt.excluded.c1, "c2": insert_stmt.excluded.c2, }, ).add_cte(delete_statement_cte) print(update_statement)
The above statement renders as:
WITH deletions AS ( DELETE FROM t WHERE t.c1 < %(c1_1)s ) INSERT INTO t (c1, c2) VALUES (%(c1)s, %(c2)s) ON CONFLICT (c1) DO UPDATE SET c1 = excluded.c1, c2 = excluded.c2
New in version 1.4.21.
- Parameters:
*ctes¶ –
zero or more
CTE
constructs.Changed in version 2.0: Multiple CTE instances are accepted
nest_here¶ –
if True, the given CTE or CTEs will be rendered as though they specified the
HasCTE.cte.nesting
flag toTrue
when they were added to thisHasCTE
. Assuming the given CTEs are not referenced in an outer-enclosing statement as well, the CTEs given should render at the level of this statement when this flag is given.New in version 2.0.
See also
-
method
sqlalchemy.sql.expression.Select.
alias(name: str | None = None, flat: bool = False) → Subquery¶ inherited from the
SelectBase.alias()
method ofSelectBase
Return a named subquery against this
SelectBase
.For a
SelectBase
(as opposed to aFromClause
), this returns aSubquery
object which behaves mostly the same as theAlias
object that is used with aFromClause
.Changed in version 1.4: The
SelectBase.alias()
method is now a synonym for theSelectBase.subquery()
method.
-
method
sqlalchemy.sql.expression.Select.
as_scalar() → ScalarSelect[Any]¶ inherited from the
SelectBase.as_scalar()
method ofSelectBase
Deprecated since version 1.4: The
SelectBase.as_scalar()
method is deprecated and will be removed in a future release. Please refer toSelectBase.scalar_subquery()
.
-
attribute
sqlalchemy.sql.expression.Select.
c¶ inherited from the
SelectBase.c
attribute ofSelectBase
Deprecated since version 1.4: The
SelectBase.c
andSelectBase.columns
attributes are deprecated and will be removed in a future release; these attributes implicitly create a subquery that should be explicit. Please callSelectBase.subquery()
first in order to create a subquery, which then contains this attribute. To access the columns that this SELECT object SELECTs from, use theSelectBase.selected_columns
attribute.
-
method
sqlalchemy.sql.expression.Select.
column(column: _ColumnsClauseArgument[Any]) → Select[Any]¶ Return a new
select()
construct with the given column expression added to its columns clause.Deprecated since version 1.4: The
Select.column()
method is deprecated and will be removed in a future release. Please useSelect.add_columns()
E.g.:
my_select = my_select.column(table.c.new_column)
See the documentation for
Select.with_only_columns()
for guidelines on adding /replacing the columns of aSelect
object.
-
attribute
sqlalchemy.sql.expression.Select.
column_descriptions¶ Return a plugin-enabled ‘column descriptions’ structure referring to the columns which are SELECTed by this statement.
This attribute is generally useful when using the ORM, as an extended structure which includes information about mapped entities is returned. The section Inspecting entities and columns from ORM-enabled SELECT and DML statements contains more background.
For a Core-only statement, the structure returned by this accessor is derived from the same objects that are returned by the
Select.selected_columns
accessor, formatted as a list of dictionaries which contain the keysname
,type
andexpr
, which indicate the column expressions to be selected:>>> stmt = select(user_table) >>> stmt.column_descriptions [ { 'name': 'id', 'type': Integer(), 'expr': Column('id', Integer(), ...)}, { 'name': 'name', 'type': String(length=30), 'expr': Column('name', String(length=30), ...)} ]
Changed in version 1.4.33: The
Select.column_descriptions
attribute returns a structure for a Core-only set of entities, not just ORM-only entities.See also
UpdateBase.entity_description
- entity information for aninsert()
,update()
, ordelete()
Inspecting entities and columns from ORM-enabled SELECT and DML statements - ORM background
-
attribute
sqlalchemy.sql.expression.Select.
columns_clause_froms¶ Return the set of
FromClause
objects implied by the columns clause of this SELECT statement.New in version 1.4.23.
See also
Select.froms
- “final” FROM list taking the full statement into accountSelect.with_only_columns()
- makes use of this collection to set up a new FROM list
-
method
sqlalchemy.sql.expression.Select.
correlate(*fromclauses: Literal[None, False] | _FromClauseArgument) → Self¶ Return a new
Select
which will correlate the given FROM clauses to that of an enclosingSelect
.Calling this method turns off the
Select
object’s default behavior of “auto-correlation”. Normally, FROM elements which appear in aSelect
that encloses this one via its WHERE clause, ORDER BY, HAVING or columns clause will be omitted from thisSelect
object’s FROM clause. Setting an explicit correlation collection using theSelect.correlate()
method provides a fixed list of FROM objects that can potentially take place in this process.When
Select.correlate()
is used to apply specific FROM clauses for correlation, the FROM elements become candidates for correlation regardless of how deeply nested thisSelect
object is, relative to an enclosingSelect
which refers to the same FROM object. This is in contrast to the behavior of “auto-correlation” which only correlates to an immediate enclosingSelect
. Multi-level correlation ensures that the link between enclosed and enclosingSelect
is always via at least one WHERE/ORDER BY/HAVING/columns clause in order for correlation to take place.If
None
is passed, theSelect
object will correlate none of its FROM entries, and all will render unconditionally in the local FROM clause.- Parameters:
*fromclauses¶ – one or more
FromClause
or other FROM-compatible construct such as an ORM mapped entity to become part of the correlate collection; alternatively pass a single valueNone
to remove all existing correlations.
-
method
sqlalchemy.sql.expression.Select.
correlate_except(*fromclauses: Literal[None, False] | _FromClauseArgument) → Self¶ Return a new
Select
which will omit the given FROM clauses from the auto-correlation process.Calling
Select.correlate_except()
turns off theSelect
object’s default behavior of “auto-correlation” for the given FROM elements. An element specified here will unconditionally appear in the FROM list, while all other FROM elements remain subject to normal auto-correlation behaviors.If
None
is passed, or no arguments are passed, theSelect
object will correlate all of its FROM entries.- Parameters:
*fromclauses¶ – a list of one or more
FromClause
constructs, or other compatible constructs (i.e. ORM-mapped classes) to become part of the correlate-exception collection.
-
method
sqlalchemy.sql.expression.Select.
corresponding_column(column: KeyedColumnElement[Any], require_embedded: bool = False) → KeyedColumnElement[Any] | None¶ inherited from the
Selectable.corresponding_column()
method ofSelectable
Given a
ColumnElement
, return the exportedColumnElement
object from theSelectable.exported_columns
collection of thisSelectable
which corresponds to that originalColumnElement
via a common ancestor column.- Parameters:
column¶ – the target
ColumnElement
to be matched.require_embedded¶ – only return corresponding columns for the given
ColumnElement
, if the givenColumnElement
is actually present within a sub-element of thisSelectable
. Normally the column will match if it merely shares a common ancestor with one of the exported columns of thisSelectable
.
See also
Selectable.exported_columns
- theColumnCollection
that is used for the operation.ColumnCollection.corresponding_column()
- implementation method.
-
method
sqlalchemy.sql.expression.Select.
cte(name: str | None = None, recursive: bool = False, nesting: bool = False) → CTE¶ inherited from the
HasCTE.cte()
method ofHasCTE
Return a new
CTE
, or Common Table Expression instance.Common table expressions are a SQL standard whereby SELECT statements can draw upon secondary statements specified along with the primary statement, using a clause called “WITH”. Special semantics regarding UNION can also be employed to allow “recursive” queries, where a SELECT statement can draw upon the set of rows that have previously been selected.
CTEs can also be applied to DML constructs UPDATE, INSERT and DELETE on some databases, both as a source of CTE rows when combined with RETURNING, as well as a consumer of CTE rows.
SQLAlchemy detects
CTE
objects, which are treated similarly toAlias
objects, as special elements to be delivered to the FROM clause of the statement as well as to a WITH clause at the top of the statement.For special prefixes such as PostgreSQL “MATERIALIZED” and “NOT MATERIALIZED”, the
CTE.prefix_with()
method may be used to establish these.Changed in version 1.3.13: Added support for prefixes. In particular - MATERIALIZED and NOT MATERIALIZED.
- Parameters:
name¶ – name given to the common table expression. Like
FromClause.alias()
, the name can be left asNone
in which case an anonymous symbol will be used at query compile time.recursive¶ – if
True
, will renderWITH RECURSIVE
. A recursive common table expression is intended to be used in conjunction with UNION ALL in order to derive rows from those already selected.nesting¶ –
if
True
, will render the CTE locally to the statement in which it is referenced. For more complex scenarios, theHasCTE.add_cte()
method using theHasCTE.add_cte.nest_here
parameter may also be used to more carefully control the exact placement of a particular CTE.New in version 1.4.24.
See also
The following examples include two from PostgreSQL’s documentation at https://www.postgresql.org/docs/current/static/queries-with.html, as well as additional examples.
Example 1, non recursive:
from sqlalchemy import ( Table, Column, String, Integer, MetaData, select, func, ) metadata = MetaData() orders = Table( "orders", metadata, Column("region", String), Column("amount", Integer), Column("product", String), Column("quantity", Integer), ) regional_sales = ( select(orders.c.region, func.sum(orders.c.amount).label("total_sales")) .group_by(orders.c.region) .cte("regional_sales") ) top_regions = ( select(regional_sales.c.region) .where( regional_sales.c.total_sales > select(func.sum(regional_sales.c.total_sales) / 10) ) .cte("top_regions") ) statement = ( select( orders.c.region, orders.c.product, func.sum(orders.c.quantity).label("product_units"), func.sum(orders.c.amount).label("product_sales"), ) .where(orders.c.region.in_(select(top_regions.c.region))) .group_by(orders.c.region, orders.c.product) ) result = conn.execute(statement).fetchall()
Example 2, WITH RECURSIVE:
from sqlalchemy import ( Table, Column, String, Integer, MetaData, select, func, ) metadata = MetaData() parts = Table( "parts", metadata, Column("part", String), Column("sub_part", String), Column("quantity", Integer), ) included_parts = ( select(parts.c.sub_part, parts.c.part, parts.c.quantity) .where(parts.c.part == "our part") .cte(recursive=True) ) incl_alias = included_parts.alias() parts_alias = parts.alias() included_parts = included_parts.union_all( select( parts_alias.c.sub_part, parts_alias.c.part, parts_alias.c.quantity ).where(parts_alias.c.part == incl_alias.c.sub_part) ) statement = select( included_parts.c.sub_part, func.sum(included_parts.c.quantity).label("total_quantity"), ).group_by(included_parts.c.sub_part) result = conn.execute(statement).fetchall()
Example 3, an upsert using UPDATE and INSERT with CTEs:
from datetime import date from sqlalchemy import ( MetaData, Table, Column, Integer, Date, select, literal, and_, exists, ) metadata = MetaData() visitors = Table( "visitors", metadata, Column("product_id", Integer, primary_key=True), Column("date", Date, primary_key=True), Column("count", Integer), ) # add 5 visitors for the product_id == 1 product_id = 1 day = date.today() count = 5 update_cte = ( visitors.update() .where( and_(visitors.c.product_id == product_id, visitors.c.date == day) ) .values(count=visitors.c.count + count) .returning(literal(1)) .cte("update_cte") ) upsert = visitors.insert().from_select( [visitors.c.product_id, visitors.c.date, visitors.c.count], select(literal(product_id), literal(day), literal(count)).where( ~exists(update_cte.select()) ), ) connection.execute(upsert)
Example 4, Nesting CTE (SQLAlchemy 1.4.24 and above):
value_a = select(literal("root").label("n")).cte("value_a") # A nested CTE with the same name as the root one value_a_nested = select(literal("nesting").label("n")).cte( "value_a", nesting=True ) # Nesting CTEs takes ascendency locally # over the CTEs at a higher level value_b = select(value_a_nested.c.n).cte("value_b") value_ab = select(value_a.c.n.label("a"), value_b.c.n.label("b"))
The above query will render the second CTE nested inside the first, shown with inline parameters below as:
WITH value_a AS (SELECT 'root' AS n), value_b AS (WITH value_a AS (SELECT 'nesting' AS n) SELECT value_a.n AS n FROM value_a) SELECT value_a.n AS a, value_b.n AS b FROM value_a, value_b
The same CTE can be set up using the
HasCTE.add_cte()
method as follows (SQLAlchemy 2.0 and above):value_a = select(literal("root").label("n")).cte("value_a") # A nested CTE with the same name as the root one value_a_nested = select(literal("nesting").label("n")).cte("value_a") # Nesting CTEs takes ascendency locally # over the CTEs at a higher level value_b = ( select(value_a_nested.c.n) .add_cte(value_a_nested, nest_here=True) .cte("value_b") ) value_ab = select(value_a.c.n.label("a"), value_b.c.n.label("b"))
Example 5, Non-Linear CTE (SQLAlchemy 1.4.28 and above):
edge = Table( "edge", metadata, Column("id", Integer, primary_key=True), Column("left", Integer), Column("right", Integer), ) root_node = select(literal(1).label("node")).cte("nodes", recursive=True) left_edge = select(edge.c.left).join( root_node, edge.c.right == root_node.c.node ) right_edge = select(edge.c.right).join( root_node, edge.c.left == root_node.c.node ) subgraph_cte = root_node.union(left_edge, right_edge) subgraph = select(subgraph_cte)
The above query will render 2 UNIONs inside the recursive CTE:
WITH RECURSIVE nodes(node) AS ( SELECT 1 AS node UNION SELECT edge."left" AS "left" FROM edge JOIN nodes ON edge."right" = nodes.node UNION SELECT edge."right" AS "right" FROM edge JOIN nodes ON edge."left" = nodes.node ) SELECT nodes.node FROM nodes
See also
Query.cte()
- ORM version ofHasCTE.cte()
.
-
method
sqlalchemy.sql.expression.Select.
distinct(*expr: _ColumnExpressionArgument[Any]) → Self¶ Return a new
select()
construct which will apply DISTINCT to the SELECT statement overall.E.g.:
from sqlalchemy import select stmt = select(users_table.c.id, users_table.c.name).distinct()
The above would produce an statement resembling:
SELECT DISTINCT user.id, user.name FROM user
The method also accepts an
*expr
parameter which produces the PostgreSQL dialect-specificDISTINCT ON
expression. Using this parameter on other backends which don’t support this syntax will raise an error.- Parameters:
*expr¶ –
optional column expressions. When present, the PostgreSQL dialect will render a
DISTINCT ON (<expressions>)
construct. A deprecation warning and/orCompileError
will be raised on other backends.Deprecated since version 1.4: Using *expr in other dialects is deprecated and will raise
CompileError
in a future version.
-
method
sqlalchemy.sql.expression.Select.
except_(*other: _SelectStatementForCompoundArgument) → CompoundSelect¶ Return a SQL
EXCEPT
of this select() construct against the given selectable provided as positional arguments.- Parameters:
*other¶ –
one or more elements with which to create a UNION.
Changed in version 1.4.28: multiple elements are now accepted.
-
method
sqlalchemy.sql.expression.Select.
except_all(*other: _SelectStatementForCompoundArgument) → CompoundSelect¶ Return a SQL
EXCEPT ALL
of this select() construct against the given selectables provided as positional arguments.- Parameters:
*other¶ –
one or more elements with which to create a UNION.
Changed in version 1.4.28: multiple elements are now accepted.
-
method
sqlalchemy.sql.expression.Select.
execution_options(**kw: Any) → Self¶ inherited from the
Executable.execution_options()
method ofExecutable
Set non-SQL options for the statement which take effect during execution.
Execution options can be set at many scopes, including per-statement, per-connection, or per execution, using methods such as
Connection.execution_options()
and parameters which accept a dictionary of options such asConnection.execute.execution_options
andSession.execute.execution_options
.The primary characteristic of an execution option, as opposed to other kinds of options such as ORM loader options, is that execution options never affect the compiled SQL of a query, only things that affect how the SQL statement itself is invoked or how results are fetched. That is, execution options are not part of what’s accommodated by SQL compilation nor are they considered part of the cached state of a statement.
The
Executable.execution_options()
method is generative, as is the case for the method as applied to theEngine
andQuery
objects, which means when the method is called, a copy of the object is returned, which applies the given parameters to that new copy, but leaves the original unchanged:statement = select(table.c.x, table.c.y) new_statement = statement.execution_options(my_option=True)
An exception to this behavior is the
Connection
object, where theConnection.execution_options()
method is explicitly not generative.The kinds of options that may be passed to
Executable.execution_options()
and other related methods and parameter dictionaries include parameters that are explicitly consumed by SQLAlchemy Core or ORM, as well as arbitrary keyword arguments not defined by SQLAlchemy, which means the methods and/or parameter dictionaries may be used for user-defined parameters that interact with custom code, which may access the parameters using methods such asExecutable.get_execution_options()
andConnection.get_execution_options()
, or within selected event hooks using a dedicatedexecution_options
event parameter such asConnectionEvents.before_execute.execution_options
orORMExecuteState.execution_options
, e.g.:from sqlalchemy import event @event.listens_for(some_engine, "before_execute") def _process_opt(conn, statement, multiparams, params, execution_options): "run a SQL function before invoking a statement" if execution_options.get("do_special_thing", False): conn.exec_driver_sql("run_special_function()")
Within the scope of options that are explicitly recognized by SQLAlchemy, most apply to specific classes of objects and not others. The most common execution options include:
Connection.execution_options.isolation_level
- sets the isolation level for a connection or a class of connections via anEngine
. This option is accepted only byConnection
orEngine
.Connection.execution_options.stream_results
- indicates results should be fetched using a server side cursor; this option is accepted byConnection
, by theConnection.execute.execution_options
parameter onConnection.execute()
, and additionally byExecutable.execution_options()
on a SQL statement object, as well as by ORM constructs likeSession.execute()
.Connection.execution_options.compiled_cache
- indicates a dictionary that will serve as the SQL compilation cache for aConnection
orEngine
, as well as for ORM methods likeSession.execute()
. Can be passed asNone
to disable caching for statements. This option is not accepted byExecutable.execution_options()
as it is inadvisable to carry along a compilation cache within a statement object.Connection.execution_options.schema_translate_map
- a mapping of schema names used by the Schema Translate Map feature, accepted byConnection
,Engine
,Executable
, as well as by ORM constructs likeSession.execute()
.
See also
Connection.execution_options()
Connection.execute.execution_options
Session.execute.execution_options
ORM Execution Options - documentation on all ORM-specific execution options
-
method
sqlalchemy.sql.expression.Select.
exists() → Exists¶ inherited from the
SelectBase.exists()
method ofSelectBase
Return an
Exists
representation of this selectable, which can be used as a column expression.The returned object is an instance of
Exists
.New in version 1.4.
-
attribute
sqlalchemy.sql.expression.Select.
exported_columns¶ inherited from the
SelectBase.exported_columns
attribute ofSelectBase
A
ColumnCollection
that represents the “exported” columns of thisSelectable
, not includingTextClause
constructs.The “exported” columns for a
SelectBase
object are synonymous with theSelectBase.selected_columns
collection.New in version 1.4.
-
method
sqlalchemy.sql.expression.Select.
fetch(count: _LimitOffsetType, with_ties: bool = False, percent: bool = False) → Self¶ inherited from the
GenerativeSelect.fetch()
method ofGenerativeSelect
Return a new selectable with the given FETCH FIRST criterion applied.
This is a numeric value which usually renders as
FETCH {FIRST | NEXT} [ count ] {ROW | ROWS} {ONLY | WITH TIES}
expression in the resulting select. This functionality is is currently implemented for Oracle Database, PostgreSQL, MSSQL.Use
GenerativeSelect.offset()
to specify the offset.Note
The
GenerativeSelect.fetch()
method will replace any clause applied withGenerativeSelect.limit()
.New in version 1.4.
- Parameters:
count¶ – an integer COUNT parameter, or a SQL expression that provides an integer result. When
percent=True
this will represent the percentage of rows to return, not the absolute value. PassNone
to reset it.with_ties¶ – When
True
, the WITH TIES option is used to return any additional rows that tie for the last place in the result set according to theORDER BY
clause. TheORDER BY
may be mandatory in this case. Defaults toFalse
percent¶ – When
True
,count
represents the percentage of the total number of selected rows to return. Defaults toFalse
-
method
sqlalchemy.sql.expression.Select.
filter(*criteria: _ColumnExpressionArgument[bool]) → Self¶ A synonym for the
Select.where()
method.
-
method
sqlalchemy.sql.expression.Select.
filter_by(**kwargs: Any) → Self¶ apply the given filtering criterion as a WHERE clause to this select.
-
method
sqlalchemy.sql.expression.Select.
from_statement(statement: ReturnsRowsRole) → ExecutableReturnsRows¶ Apply the columns which this
Select
would select onto another statement.This operation is plugin-specific and will raise a not supported exception if this
Select
does not select from plugin-enabled entities.The statement is typically either a
text()
orselect()
construct, and should return the set of columns appropriate to the entities represented by thisSelect
.See also
Getting ORM Results from Textual Statements - usage examples in the ORM Querying Guide
-
attribute
sqlalchemy.sql.expression.Select.
froms¶ Return the displayed list of
FromClause
elements.Deprecated since version 1.4.23: The
Select.froms
attribute is moved to theSelect.get_final_froms()
method.
-
method
sqlalchemy.sql.expression.Select.
get_children(**kw: Any) → Iterable[ClauseElement]¶ Return immediate child
HasTraverseInternals
elements of thisHasTraverseInternals
.This is used for visit traversal.
**kw may contain flags that change the collection that is returned, for example to return a subset of items in order to cut down on larger traversals, or to return child items from a different context (such as schema-level collections instead of clause-level).
-
method
sqlalchemy.sql.expression.Select.
get_execution_options() → _ExecuteOptions¶ inherited from the
Executable.get_execution_options()
method ofExecutable
Get the non-SQL options which will take effect during execution.
New in version 1.3.
See also
-
method
sqlalchemy.sql.expression.Select.
get_final_froms() → Sequence[FromClause]¶ Compute the final displayed list of
FromClause
elements.This method will run through the full computation required to determine what FROM elements will be displayed in the resulting SELECT statement, including shadowing individual tables with JOIN objects, as well as full computation for ORM use cases including eager loading clauses.
For ORM use, this accessor returns the post compilation list of FROM objects; this collection will include elements such as eagerly loaded tables and joins. The objects will not be ORM enabled and not work as a replacement for the
Select.select_froms()
collection; additionally, the method is not well performing for an ORM enabled statement as it will incur the full ORM construction process.To retrieve the FROM list that’s implied by the “columns” collection passed to the
Select
originally, use theSelect.columns_clause_froms
accessor.To select from an alternative set of columns while maintaining the FROM list, use the
Select.with_only_columns()
method and pass theSelect.with_only_columns.maintain_column_froms
parameter.New in version 1.4.23: - the
Select.get_final_froms()
method replaces the previousSelect.froms
accessor, which is deprecated.See also
-
method
sqlalchemy.sql.expression.Select.
get_label_style() → SelectLabelStyle¶ inherited from the
GenerativeSelect.get_label_style()
method ofGenerativeSelect
Retrieve the current label style.
New in version 1.4.
-
method
sqlalchemy.sql.expression.Select.
group_by(_GenerativeSelect__first: Literal[None, _NoArg.NO_ARG] | _ColumnExpressionOrStrLabelArgument[Any] = _NoArg.NO_ARG, *clauses: _ColumnExpressionOrStrLabelArgument[Any]) → Self¶ inherited from the
GenerativeSelect.group_by()
method ofGenerativeSelect
Return a new selectable with the given list of GROUP BY criterion applied.
All existing GROUP BY settings can be suppressed by passing
None
.e.g.:
stmt = select(table.c.name, func.max(table.c.stat)).group_by(table.c.name)
- Parameters:
*clauses¶ – a series of
ColumnElement
constructs which will be used to generate an GROUP BY clause.
-
method
sqlalchemy.sql.expression.Select.
having(*having: _ColumnExpressionArgument[bool]) → Self¶ Return a new
select()
construct with the given expression added to its HAVING clause, joined to the existing clause via AND, if any.
-
attribute
sqlalchemy.sql.expression.Select.
inherit_cache: bool | None = None¶ inherited from the
HasCacheKey.inherit_cache
attribute ofHasCacheKey
Indicate if this
HasCacheKey
instance should make use of the cache key generation scheme used by its immediate superclass.The attribute defaults to
None
, which indicates that a construct has not yet taken into account whether or not its appropriate for it to participate in caching; this is functionally equivalent to setting the value toFalse
, except that a warning is also emitted.This flag can be set to
True
on a particular class, if the SQL that corresponds to the object does not change based on attributes which are local to this class, and not its superclass.See also
Enabling Caching Support for Custom Constructs - General guideslines for setting the
HasCacheKey.inherit_cache
attribute for third-party or user defined SQL constructs.
-
attribute
sqlalchemy.sql.expression.Select.
inner_columns¶ An iterator of all
ColumnElement
expressions which would be rendered into the columns clause of the resulting SELECT statement.This method is legacy as of 1.4 and is superseded by the
Select.exported_columns
collection.
-
method
sqlalchemy.sql.expression.Select.
intersect(*other: _SelectStatementForCompoundArgument) → CompoundSelect¶ Return a SQL
INTERSECT
of this select() construct against the given selectables provided as positional arguments.- Parameters:
*other¶ –
one or more elements with which to create a UNION.
Changed in version 1.4.28: multiple elements are now accepted.
**kwargs¶ – keyword arguments are forwarded to the constructor for the newly created
CompoundSelect
object.
-
method
sqlalchemy.sql.expression.Select.
intersect_all(*other: _SelectStatementForCompoundArgument) → CompoundSelect¶ Return a SQL
INTERSECT ALL
of this select() construct against the given selectables provided as positional arguments.- Parameters:
*other¶ –
one or more elements with which to create a UNION.
Changed in version 1.4.28: multiple elements are now accepted.
**kwargs¶ – keyword arguments are forwarded to the constructor for the newly created
CompoundSelect
object.
-
method
sqlalchemy.sql.expression.Select.
is_derived_from(fromclause: FromClause | None) → bool¶ Return
True
if thisReturnsRows
is ‘derived’ from the givenFromClause
.An example would be an Alias of a Table is derived from that Table.
-
method
sqlalchemy.sql.expression.Select.
join(target: _JoinTargetArgument, onclause: _OnClauseArgument | None = None, *, isouter: bool = False, full: bool = False) → Self¶ Create a SQL JOIN against this
Select
object’s criterion and apply generatively, returning the newly resultingSelect
.E.g.:
stmt = select(user_table).join( address_table, user_table.c.id == address_table.c.user_id )
The above statement generates SQL similar to:
SELECT user.id, user.name FROM user JOIN address ON user.id = address.user_id
Changed in version 1.4:
Select.join()
now creates aJoin
object between aFromClause
source that is within the FROM clause of the existing SELECT, and a given targetFromClause
, and then adds thisJoin
to the FROM clause of the newly generated SELECT statement. This is completely reworked from the behavior in 1.3, which would instead create a subquery of the entireSelect
and then join that subquery to the target.This is a backwards incompatible change as the previous behavior was mostly useless, producing an unnamed subquery rejected by most databases in any case. The new behavior is modeled after that of the very successful
Query.join()
method in the ORM, in order to support the functionality ofQuery
being available by using aSelect
object with anSession
.See the notes for this change at select().join() and outerjoin() add JOIN criteria to the current query, rather than creating a subquery.
- Parameters:
target¶ – target table to join towards
onclause¶ – ON clause of the join. If omitted, an ON clause is generated automatically based on the
ForeignKey
linkages between the two tables, if one can be unambiguously determined, otherwise an error is raised.isouter¶ – if True, generate LEFT OUTER join. Same as
Select.outerjoin()
.full¶ – if True, generate FULL OUTER join.
See also
Explicit FROM clauses and JOINs - in the SQLAlchemy Unified Tutorial
Joins - in the ORM Querying Guide
-
method
sqlalchemy.sql.expression.Select.
join_from(from_: _FromClauseArgument, target: _JoinTargetArgument, onclause: _OnClauseArgument | None = None, *, isouter: bool = False, full: bool = False) → Self¶ Create a SQL JOIN against this
Select
object’s criterion and apply generatively, returning the newly resultingSelect
.E.g.:
stmt = select(user_table, address_table).join_from( user_table, address_table, user_table.c.id == address_table.c.user_id )
The above statement generates SQL similar to:
SELECT user.id, user.name, address.id, address.email, address.user_id FROM user JOIN address ON user.id = address.user_id
New in version 1.4.
- Parameters:
from_¶ – the left side of the join, will be rendered in the FROM clause and is roughly equivalent to using the
Select.select_from()
method.target¶ – target table to join towards
onclause¶ – ON clause of the join.
isouter¶ – if True, generate LEFT OUTER join. Same as
Select.outerjoin()
.full¶ – if True, generate FULL OUTER join.
See also
Explicit FROM clauses and JOINs - in the SQLAlchemy Unified Tutorial
Joins - in the ORM Querying Guide
-
method
sqlalchemy.sql.expression.Select.
label(name: str | None) → Label[Any]¶ inherited from the
SelectBase.label()
method ofSelectBase
Return a ‘scalar’ representation of this selectable, embedded as a subquery with a label.
See also
-
method
sqlalchemy.sql.expression.Select.
lateral(name: str | None = None) → LateralFromClause¶ inherited from the
SelectBase.lateral()
method ofSelectBase
Return a LATERAL alias of this
Selectable
.The return value is the
Lateral
construct also provided by the top-levellateral()
function.See also
LATERAL correlation - overview of usage.
-
method
sqlalchemy.sql.expression.Select.
limit(limit: _LimitOffsetType) → Self¶ inherited from the
GenerativeSelect.limit()
method ofGenerativeSelect
Return a new selectable with the given LIMIT criterion applied.
This is a numerical value which usually renders as a
LIMIT
expression in the resulting select. Backends that don’t supportLIMIT
will attempt to provide similar functionality.Note
The
GenerativeSelect.limit()
method will replace any clause applied withGenerativeSelect.fetch()
.- Parameters:
limit¶ – an integer LIMIT parameter, or a SQL expression that provides an integer result. Pass
None
to reset it.
-
method
sqlalchemy.sql.expression.Select.
offset(offset: _LimitOffsetType) → Self¶ inherited from the
GenerativeSelect.offset()
method ofGenerativeSelect
Return a new selectable with the given OFFSET criterion applied.
This is a numeric value which usually renders as an
OFFSET
expression in the resulting select. Backends that don’t supportOFFSET
will attempt to provide similar functionality.- Parameters:
offset¶ – an integer OFFSET parameter, or a SQL expression that provides an integer result. Pass
None
to reset it.
-
method
sqlalchemy.sql.expression.Select.
options(*options: ExecutableOption) → Self¶ inherited from the
Executable.options()
method ofExecutable
Apply options to this statement.
In the general sense, options are any kind of Python object that can be interpreted by the SQL compiler for the statement. These options can be consumed by specific dialects or specific kinds of compilers.
The most commonly known kind of option are the ORM level options that apply “eager load” and other loading behaviors to an ORM query. However, options can theoretically be used for many other purposes.
For background on specific kinds of options for specific kinds of statements, refer to the documentation for those option objects.
Changed in version 1.4: - added
Executable.options()
to Core statement objects towards the goal of allowing unified Core / ORM querying capabilities.See also
Column Loading Options - refers to options specific to the usage of ORM queries
Relationship Loading with Loader Options - refers to options specific to the usage of ORM queries
-
method
sqlalchemy.sql.expression.Select.
order_by(_GenerativeSelect__first: Literal[None, _NoArg.NO_ARG] | _ColumnExpressionOrStrLabelArgument[Any] = _NoArg.NO_ARG, *clauses: _ColumnExpressionOrStrLabelArgument[Any]) → Self¶ inherited from the
GenerativeSelect.order_by()
method ofGenerativeSelect
Return a new selectable with the given list of ORDER BY criteria applied.
e.g.:
stmt = select(table).order_by(table.c.id, table.c.name)
Calling this method multiple times is equivalent to calling it once with all the clauses concatenated. All existing ORDER BY criteria may be cancelled by passing
None
by itself. New ORDER BY criteria may then be added by invokingQuery.order_by()
again, e.g.:# will erase all ORDER BY and ORDER BY new_col alone stmt = stmt.order_by(None).order_by(new_col)
- Parameters:
*clauses¶ – a series of
ColumnElement
constructs which will be used to generate an ORDER BY clause.
See also
ORDER BY - in the SQLAlchemy Unified Tutorial
Ordering or Grouping by a Label - in the SQLAlchemy Unified Tutorial
-
method
sqlalchemy.sql.expression.Select.
outerjoin(target: _JoinTargetArgument, onclause: _OnClauseArgument | None = None, *, full: bool = False) → Self¶ Create a left outer join.
Parameters are the same as that of
Select.join()
.Changed in version 1.4:
Select.outerjoin()
now creates aJoin
object between aFromClause
source that is within the FROM clause of the existing SELECT, and a given targetFromClause
, and then adds thisJoin
to the FROM clause of the newly generated SELECT statement. This is completely reworked from the behavior in 1.3, which would instead create a subquery of the entireSelect
and then join that subquery to the target.This is a backwards incompatible change as the previous behavior was mostly useless, producing an unnamed subquery rejected by most databases in any case. The new behavior is modeled after that of the very successful
Query.join()
method in the ORM, in order to support the functionality ofQuery
being available by using aSelect
object with anSession
.See the notes for this change at select().join() and outerjoin() add JOIN criteria to the current query, rather than creating a subquery.
See also
Explicit FROM clauses and JOINs - in the SQLAlchemy Unified Tutorial
Joins - in the ORM Querying Guide
-
method
sqlalchemy.sql.expression.Select.
outerjoin_from(from_: _FromClauseArgument, target: _JoinTargetArgument, onclause: _OnClauseArgument | None = None, *, full: bool = False) → Self¶ Create a SQL LEFT OUTER JOIN against this
Select
object’s criterion and apply generatively, returning the newly resultingSelect
.Usage is the same as that of
Select.join_from()
.
-
method
sqlalchemy.sql.expression.Select.
prefix_with(*prefixes: _TextCoercedExpressionArgument[Any], dialect: str = '*') → Self¶ inherited from the
HasPrefixes.prefix_with()
method ofHasPrefixes
Add one or more expressions following the statement keyword, i.e. SELECT, INSERT, UPDATE, or DELETE. Generative.
This is used to support backend-specific prefix keywords such as those provided by MySQL.
E.g.:
stmt = table.insert().prefix_with("LOW_PRIORITY", dialect="mysql") # MySQL 5.7 optimizer hints stmt = select(table).prefix_with("/*+ BKA(t1) */", dialect="mysql")
Multiple prefixes can be specified by multiple calls to
HasPrefixes.prefix_with()
.- Parameters:
*prefixes¶ – textual or
ClauseElement
construct which will be rendered following the INSERT, UPDATE, or DELETE keyword.dialect¶ – optional string dialect name which will limit rendering of this prefix to only that dialect.
-
method
sqlalchemy.sql.expression.Select.
reduce_columns(only_synonyms: bool = True) → Select¶ Return a new
select()
construct with redundantly named, equivalently-valued columns removed from the columns clause.“Redundant” here means two columns where one refers to the other either based on foreign key, or via a simple equality comparison in the WHERE clause of the statement. The primary purpose of this method is to automatically construct a select statement with all uniquely-named columns, without the need to use table-qualified labels as
Select.set_label_style()
does.When columns are omitted based on foreign key, the referred-to column is the one that’s kept. When columns are omitted based on WHERE equivalence, the first column in the columns clause is the one that’s kept.
- Parameters:
only_synonyms¶ – when True, limit the removal of columns to those which have the same name as the equivalent. Otherwise, all columns that are equivalent to another are removed.
-
method
sqlalchemy.sql.expression.Select.
replace_selectable(old: FromClause, alias: Alias) → Self¶ inherited from the
Selectable.replace_selectable()
method ofSelectable
Replace all occurrences of
FromClause
‘old’ with the givenAlias
object, returning a copy of thisFromClause
.Deprecated since version 1.4: The
Selectable.replace_selectable()
method is deprecated, and will be removed in a future release. Similar functionality is available via the sqlalchemy.sql.visitors module.
-
method
sqlalchemy.sql.expression.Select.
scalar_subquery() → ScalarSelect[Any]¶ inherited from the
SelectBase.scalar_subquery()
method ofSelectBase
Return a ‘scalar’ representation of this selectable, which can be used as a column expression.
The returned object is an instance of
ScalarSelect
.Typically, a select statement which has only one column in its columns clause is eligible to be used as a scalar expression. The scalar subquery can then be used in the WHERE clause or columns clause of an enclosing SELECT.
Note that the scalar subquery differentiates from the FROM-level subquery that can be produced using the
SelectBase.subquery()
method.See also
Scalar and Correlated Subqueries - in the 2.0 tutorial
-
method
sqlalchemy.sql.expression.Select.
select(*arg: Any, **kw: Any) → Select¶ inherited from the
SelectBase.select()
method ofSelectBase
Deprecated since version 1.4: The
SelectBase.select()
method is deprecated and will be removed in a future release; this method implicitly creates a subquery that should be explicit. Please callSelectBase.subquery()
first in order to create a subquery, which then can be selected.
-
method
sqlalchemy.sql.expression.Select.
select_from(*froms: _FromClauseArgument) → Self¶ Return a new
select()
construct with the given FROM expression(s) merged into its list of FROM objects.E.g.:
table1 = table("t1", column("a")) table2 = table("t2", column("b")) s = select(table1.c.a).select_from( table1.join(table2, table1.c.a == table2.c.b) )
The “from” list is a unique set on the identity of each element, so adding an already present
Table
or other selectable will have no effect. Passing aJoin
that refers to an already presentTable
or other selectable will have the effect of concealing the presence of that selectable as an individual element in the rendered FROM list, instead rendering it into a JOIN clause.While the typical purpose of
Select.select_from()
is to replace the default, derived FROM clause with a join, it can also be called with individual table elements, multiple times if desired, in the case that the FROM clause cannot be fully derived from the columns clause:select(func.count("*")).select_from(table1)
-
attribute
sqlalchemy.sql.expression.Select.
selected_columns¶ A
ColumnCollection
representing the columns that this SELECT statement or similar construct returns in its result set, not includingTextClause
constructs.This collection differs from the
FromClause.columns
collection of aFromClause
in that the columns within this collection cannot be directly nested inside another SELECT statement; a subquery must be applied first which provides for the necessary parenthesization required by SQL.For a
select()
construct, the collection here is exactly what would be rendered inside the “SELECT” statement, and theColumnElement
objects are directly present as they were given, e.g.:col1 = column("q", Integer) col2 = column("p", Integer) stmt = select(col1, col2)
Above,
stmt.selected_columns
would be a collection that contains thecol1
andcol2
objects directly. For a statement that is against aTable
or otherFromClause
, the collection will use theColumnElement
objects that are in theFromClause.c
collection of the from element.A use case for the
Select.selected_columns
collection is to allow the existing columns to be referenced when adding additional criteria, e.g.:def filter_on_id(my_select, id): return my_select.where(my_select.selected_columns["id"] == id) stmt = select(MyModel) # adds "WHERE id=:param" to the statement stmt = filter_on_id(stmt, 42)
Note
The
Select.selected_columns
collection does not include expressions established in the columns clause using thetext()
construct; these are silently omitted from the collection. To use plain textual column expressions inside of aSelect
construct, use theliteral_column()
construct.New in version 1.4.
-
method
sqlalchemy.sql.expression.Select.
self_group(against: OperatorType | None = None) → SelectStatementGrouping | Self¶ Return a ‘grouping’ construct as per the
ClauseElement
specification.This produces an element that can be embedded in an expression. Note that this method is called automatically as needed when constructing expressions and should not require explicit use.
-
method
sqlalchemy.sql.expression.Select.
set_label_style(style: SelectLabelStyle) → Self¶ inherited from the
GenerativeSelect.set_label_style()
method ofGenerativeSelect
Return a new selectable with the specified label style.
There are three “label styles” available,
SelectLabelStyle.LABEL_STYLE_DISAMBIGUATE_ONLY
,SelectLabelStyle.LABEL_STYLE_TABLENAME_PLUS_COL
, andSelectLabelStyle.LABEL_STYLE_NONE
. The default style isSelectLabelStyle.LABEL_STYLE_DISAMBIGUATE_ONLY
.In modern SQLAlchemy, there is not generally a need to change the labeling style, as per-expression labels are more effectively used by making use of the
ColumnElement.label()
method. In past versions,LABEL_STYLE_TABLENAME_PLUS_COL
was used to disambiguate same-named columns from different tables, aliases, or subqueries; the newerLABEL_STYLE_DISAMBIGUATE_ONLY
now applies labels only to names that conflict with an existing name so that the impact of this labeling is minimal.The rationale for disambiguation is mostly so that all column expressions are available from a given
FromClause.c
collection when a subquery is created.New in version 1.4: - the
GenerativeSelect.set_label_style()
method replaces the previous combination of.apply_labels()
,.with_labels()
anduse_labels=True
methods and/or parameters.See also
LABEL_STYLE_DISAMBIGUATE_ONLY
LABEL_STYLE_TABLENAME_PLUS_COL
LABEL_STYLE_NONE
LABEL_STYLE_DEFAULT
-
method
sqlalchemy.sql.expression.Select.
slice(start: int, stop: int) → Self¶ inherited from the
GenerativeSelect.slice()
method ofGenerativeSelect
Apply LIMIT / OFFSET to this statement based on a slice.
The start and stop indices behave like the argument to Python’s built-in
range()
function. This method provides an alternative to usingLIMIT
/OFFSET
to get a slice of the query.For example,
stmt = select(User).order_by(User.id).slice(1, 3)
renders as
SELECT users.id AS users_id, users.name AS users_name FROM users ORDER BY users.id LIMIT ? OFFSET ? (2, 1)
Note
The
GenerativeSelect.slice()
method will replace any clause applied withGenerativeSelect.fetch()
.New in version 1.4: Added the
GenerativeSelect.slice()
method generalized from the ORM.
-
method
sqlalchemy.sql.expression.Select.
subquery(name: str | None = None) → Subquery¶ inherited from the
SelectBase.subquery()
method ofSelectBase
Return a subquery of this
SelectBase
.A subquery is from a SQL perspective a parenthesized, named construct that can be placed in the FROM clause of another SELECT statement.
Given a SELECT statement such as:
stmt = select(table.c.id, table.c.name)
The above statement might look like:
SELECT table.id, table.name FROM table
The subquery form by itself renders the same way, however when embedded into the FROM clause of another SELECT statement, it becomes a named sub-element:
subq = stmt.subquery() new_stmt = select(subq)
The above renders as:
SELECT anon_1.id, anon_1.name FROM (SELECT table.id, table.name FROM table) AS anon_1
Historically,
SelectBase.subquery()
is equivalent to calling theFromClause.alias()
method on a FROM object; however, as aSelectBase
object is not directly FROM object, theSelectBase.subquery()
method provides clearer semantics.New in version 1.4.
-
method
sqlalchemy.sql.expression.Select.
suffix_with(*suffixes: _TextCoercedExpressionArgument[Any], dialect: str = '*') → Self¶ inherited from the
HasSuffixes.suffix_with()
method ofHasSuffixes
Add one or more expressions following the statement as a whole.
This is used to support backend-specific suffix keywords on certain constructs.
E.g.:
stmt = ( select(col1, col2) .cte() .suffix_with( "cycle empno set y_cycle to 1 default 0", dialect="oracle" ) )
Multiple suffixes can be specified by multiple calls to
HasSuffixes.suffix_with()
.- Parameters:
*suffixes¶ – textual or
ClauseElement
construct which will be rendered following the target clause.dialect¶ – Optional string dialect name which will limit rendering of this suffix to only that dialect.
-
method
sqlalchemy.sql.expression.Select.
union(*other: _SelectStatementForCompoundArgument) → CompoundSelect¶ Return a SQL
UNION
of this select() construct against the given selectables provided as positional arguments.- Parameters:
*other¶ –
one or more elements with which to create a UNION.
Changed in version 1.4.28: multiple elements are now accepted.
**kwargs¶ – keyword arguments are forwarded to the constructor for the newly created
CompoundSelect
object.
-
method
sqlalchemy.sql.expression.Select.
union_all(*other: _SelectStatementForCompoundArgument) → CompoundSelect¶ Return a SQL
UNION ALL
of this select() construct against the given selectables provided as positional arguments.- Parameters:
*other¶ –
one or more elements with which to create a UNION.
Changed in version 1.4.28: multiple elements are now accepted.
**kwargs¶ – keyword arguments are forwarded to the constructor for the newly created
CompoundSelect
object.
-
method
sqlalchemy.sql.expression.Select.
where(*whereclause: _ColumnExpressionArgument[bool]) → Self¶ Return a new
select()
construct with the given expression added to its WHERE clause, joined to the existing clause via AND, if any.
-
attribute
sqlalchemy.sql.expression.Select.
whereclause¶ Return the completed WHERE clause for this
Select
statement.This assembles the current collection of WHERE criteria into a single
BooleanClauseList
construct.New in version 1.4.
-
method
sqlalchemy.sql.expression.Select.
with_for_update(*, nowait: bool = False, read: bool = False, of: _ForUpdateOfArgument | None = None, skip_locked: bool = False, key_share: bool = False) → Self¶ inherited from the
GenerativeSelect.with_for_update()
method ofGenerativeSelect
Specify a
FOR UPDATE
clause for thisGenerativeSelect
.E.g.:
stmt = select(table).with_for_update(nowait=True)
On a database like PostgreSQL or Oracle Database, the above would render a statement like:
SELECT table.a, table.b FROM table FOR UPDATE NOWAIT
on other backends, the
nowait
option is ignored and instead would produce:SELECT table.a, table.b FROM table FOR UPDATE
When called with no arguments, the statement will render with the suffix
FOR UPDATE
. Additional arguments can then be provided which allow for common database-specific variants.- Parameters:
nowait¶ – boolean; will render
FOR UPDATE NOWAIT
on Oracle Database and PostgreSQL dialects.read¶ – boolean; will render
LOCK IN SHARE MODE
on MySQL,FOR SHARE
on PostgreSQL. On PostgreSQL, when combined withnowait
, will renderFOR SHARE NOWAIT
.of¶ – SQL expression or list of SQL expression elements, (typically
Column
objects or a compatible expression, for some backends may also be a table expression) which will render into aFOR UPDATE OF
clause; supported by PostgreSQL, Oracle Database, some MySQL versions and possibly others. May render as a table or as a column depending on backend.skip_locked¶ – boolean, will render
FOR UPDATE SKIP LOCKED
on Oracle Database and PostgreSQL dialects orFOR SHARE SKIP LOCKED
ifread=True
is also specified.key_share¶ – boolean, will render
FOR NO KEY UPDATE
, or if combined withread=True
will renderFOR KEY SHARE
, on the PostgreSQL dialect.
-
method
sqlalchemy.sql.expression.Select.
with_hint(selectable: _FromClauseArgument, text: str, dialect_name: str = '*') → Self¶ inherited from the
HasHints.with_hint()
method ofHasHints
Add an indexing or other executional context hint for the given selectable to this
Select
or other selectable object.Tip
The
Select.with_hint()
method adds hints that are specific to a single table to a statement, in a location that is dialect-specific. To add generic optimizer hints to the beginning of a statement ahead of the SELECT keyword such as for MySQL or Oracle Database, use theSelect.prefix_with()
method. To add optimizer hints to the end of a statement such as for PostgreSQL, use theSelect.with_statement_hint()
method.The text of the hint is rendered in the appropriate location for the database backend in use, relative to the given
Table
orAlias
passed as theselectable
argument. The dialect implementation typically uses Python string substitution syntax with the token%(name)s
to render the name of the table or alias. E.g. when using Oracle Database, the following:select(mytable).with_hint(mytable, "index(%(name)s ix_mytable)")
Would render SQL as:
select /*+ index(mytable ix_mytable) */ ... from mytable
The
dialect_name
option will limit the rendering of a particular hint to a particular backend. Such as, to add hints for both Oracle Database and MSSql simultaneously:select(mytable).with_hint( mytable, "index(%(name)s ix_mytable)", "oracle" ).with_hint(mytable, "WITH INDEX ix_mytable", "mssql")
See also
Select.prefix_with()
- generic SELECT prefixing which also can suit some database-specific HINT syntaxes such as MySQL or Oracle Database optimizer hints
-
method
sqlalchemy.sql.expression.Select.
with_only_columns(*entities: _ColumnsClauseArgument[Any], maintain_column_froms: bool = False, **_Select__kw: Any) → Select[Any]¶ Return a new
select()
construct with its columns clause replaced with the given entities.By default, this method is exactly equivalent to as if the original
select()
had been called with the given entities. E.g. a statement:s = select(table1.c.a, table1.c.b) s = s.with_only_columns(table1.c.b)
should be exactly equivalent to:
s = select(table1.c.b)
In this mode of operation,
Select.with_only_columns()
will also dynamically alter the FROM clause of the statement if it is not explicitly stated. To maintain the existing set of FROMs including those implied by the current columns clause, add theSelect.with_only_columns.maintain_column_froms
parameter:s = select(table1.c.a, table2.c.b) s = s.with_only_columns(table1.c.a, maintain_column_froms=True)
The above parameter performs a transfer of the effective FROMs in the columns collection to the
Select.select_from()
method, as though the following were invoked:s = select(table1.c.a, table2.c.b) s = s.select_from(table1, table2).with_only_columns(table1.c.a)
The
Select.with_only_columns.maintain_column_froms
parameter makes use of theSelect.columns_clause_froms
collection and performs an operation equivalent to the following:s = select(table1.c.a, table2.c.b) s = s.select_from(*s.columns_clause_froms).with_only_columns(table1.c.a)
- Parameters:
*entities¶ – column expressions to be used.
maintain_column_froms¶ –
boolean parameter that will ensure the FROM list implied from the current columns clause will be transferred to the
Select.select_from()
method first.New in version 1.4.23.
-
method
sqlalchemy.sql.expression.Select.
with_statement_hint(text: str, dialect_name: str = '*') → Self¶ inherited from the
HasHints.with_statement_hint()
method ofHasHints
Add a statement hint to this
Select
or other selectable object.Tip
Select.with_statement_hint()
generally adds hints at the trailing end of a SELECT statement. To place dialect-specific hints such as optimizer hints at the front of the SELECT statement after the SELECT keyword, use theSelect.prefix_with()
method for an open-ended space, or for table-specific hints theSelect.with_hint()
may be used, which places hints in a dialect-specific location.This method is similar to
Select.with_hint()
except that it does not require an individual table, and instead applies to the statement as a whole.Hints here are specific to the backend database and may include directives such as isolation levels, file directives, fetch directives, etc.
See also
Select.prefix_with()
- generic SELECT prefixing which also can suit some database-specific HINT syntaxes such as MySQL or Oracle Database optimizer hints
-
method
- class sqlalchemy.sql.expression.Selectable¶
Mark a class as being selectable.
Members
corresponding_column(), exported_columns, inherit_cache, is_derived_from(), lateral(), replace_selectable()
Class signature
class
sqlalchemy.sql.expression.Selectable
(sqlalchemy.sql.expression.ReturnsRows
)-
method
sqlalchemy.sql.expression.Selectable.
corresponding_column(column: KeyedColumnElement[Any], require_embedded: bool = False) → KeyedColumnElement[Any] | None¶ Given a
ColumnElement
, return the exportedColumnElement
object from theSelectable.exported_columns
collection of thisSelectable
which corresponds to that originalColumnElement
via a common ancestor column.- Parameters:
column¶ – the target
ColumnElement
to be matched.require_embedded¶ – only return corresponding columns for the given
ColumnElement
, if the givenColumnElement
is actually present within a sub-element of thisSelectable
. Normally the column will match if it merely shares a common ancestor with one of the exported columns of thisSelectable
.
See also
Selectable.exported_columns
- theColumnCollection
that is used for the operation.ColumnCollection.corresponding_column()
- implementation method.
-
attribute
sqlalchemy.sql.expression.Selectable.
exported_columns¶ inherited from the
ReturnsRows.exported_columns
attribute ofReturnsRows
A
ColumnCollection
that represents the “exported” columns of thisReturnsRows
.The “exported” columns represent the collection of
ColumnElement
expressions that are rendered by this SQL construct. There are primary varieties which are the “FROM clause columns” of a FROM clause, such as a table, join, or subquery, the “SELECTed columns”, which are the columns in the “columns clause” of a SELECT statement, and the RETURNING columns in a DML statement..New in version 1.4.
-
attribute
sqlalchemy.sql.expression.Selectable.
inherit_cache: bool | None = None¶ inherited from the
HasCacheKey.inherit_cache
attribute ofHasCacheKey
Indicate if this
HasCacheKey
instance should make use of the cache key generation scheme used by its immediate superclass.The attribute defaults to
None
, which indicates that a construct has not yet taken into account whether or not its appropriate for it to participate in caching; this is functionally equivalent to setting the value toFalse
, except that a warning is also emitted.This flag can be set to
True
on a particular class, if the SQL that corresponds to the object does not change based on attributes which are local to this class, and not its superclass.See also
Enabling Caching Support for Custom Constructs - General guideslines for setting the
HasCacheKey.inherit_cache
attribute for third-party or user defined SQL constructs.
-
method
sqlalchemy.sql.expression.Selectable.
is_derived_from(fromclause: FromClause | None) → bool¶ inherited from the
ReturnsRows.is_derived_from()
method ofReturnsRows
Return
True
if thisReturnsRows
is ‘derived’ from the givenFromClause
.An example would be an Alias of a Table is derived from that Table.
-
method
sqlalchemy.sql.expression.Selectable.
lateral(name: str | None = None) → LateralFromClause¶ Return a LATERAL alias of this
Selectable
.The return value is the
Lateral
construct also provided by the top-levellateral()
function.See also
LATERAL correlation - overview of usage.
-
method
sqlalchemy.sql.expression.Selectable.
replace_selectable(old: FromClause, alias: Alias) → Self¶ Replace all occurrences of
FromClause
‘old’ with the givenAlias
object, returning a copy of thisFromClause
.Deprecated since version 1.4: The
Selectable.replace_selectable()
method is deprecated, and will be removed in a future release. Similar functionality is available via the sqlalchemy.sql.visitors module.
-
method
- class sqlalchemy.sql.expression.SelectBase¶
Base class for SELECT statements.
This includes
Select
,CompoundSelect
andTextualSelect
.Members
add_cte(), alias(), as_scalar(), c, corresponding_column(), cte(), exists(), exported_columns, get_label_style(), inherit_cache, is_derived_from(), label(), lateral(), replace_selectable(), scalar_subquery(), select(), selected_columns, set_label_style(), subquery()
Class signature
class
sqlalchemy.sql.expression.SelectBase
(sqlalchemy.sql.roles.SelectStatementRole
,sqlalchemy.sql.roles.DMLSelectRole
,sqlalchemy.sql.roles.CompoundElementRole
,sqlalchemy.sql.roles.InElementRole
,sqlalchemy.sql.expression.HasCTE
,