ORM Mapped Class Configuration

Detailed reference for ORM configuration, not including relationships, which are detailed at Relationship Configuration.

For a quick look at a typical ORM configuration, start with ORM Quick Start.

For an introduction to the concept of object relational mapping as implemented in SQLAlchemy, it’s first introduced in the SQLAlchemy 1.4 / 2.0 Tutorial at Defining Table Metadata with the ORM.

• ORM Mapped Class Overview
  • ORM Mapping Styles
    • Declarative Mapping
    • Imperative Mapping
  • Mapped Class Essential Components
    • The class to be mapped
    • The table, or other from clause object
    • The properties dictionary
    • Other mapper configuration parameters
  • Mapped Class Behavior
    • Default Constructor
    • Runtime Introspection of Mapped classes, Instances and Mappers
• Mapping Classes with Declarative
  • Declarative Mapping Styles
    • Using a Generated Base Class
    • Creating an Explicit Base Non-Dynamically (for use with mypy, similar)
    • Declarative Mapping using a Decorator (no declarative base)
  • Table Configuration with Declarative
    • Declarative Table
    • Declarative with Imperative Table (a.k.a. Hybrid Declarative)
    • Mapping Declaratively with Reflected Tables
  • Mapper Configuration with Declarative
    • Defining Mapped Properties with Declarative
    • Mapper Configuration Options with Declarative
    • Other Declarative Mapping Directives
  • Composing Mapped Hierarchies with Mixins
    • Augmenting the Base
    • Mixing in Columns
    • Mixing in Relationships
    • Mixing in deferred(), column_property(), and other MapperProperty classes
    • Controlling table inheritance with mixins
    • Mixing in Columns in Inheritance Scenarios
    • Combining Table/Mapper Arguments from Multiple Mixins
    • Creating Indexes with Mixins
• Integration with dataclasses and attrs
  • Applying ORM Mappings to an existing dataclass
    • Mapping dataclasses using Declarative With Imperative Table
    • Mapping dataclasses using Declarative Mapping
    • Mapping dataclasses using Imperative Mapping
  • Applying ORM mappings to an existing attrs class
    • Mapping attrs with Declarative “Imperative Table”
    • Mapping attrs with Imperative Mapping
• Mapping Columns and Expressions
  • Mapping Table Columns
    • Naming Columns Distinctly from Attribute Names
    • Automating Column Naming Schemes from Reflected Tables
    • Using column_property for column level options
    • Mapping to an Explicit Set of Primary Key Columns
    • Mapping a Subset of Table Columns
  • SQL Expressions as Mapped Attributes
    • Using a Hybrid
    • Using column_property
    • Using a plain descriptor
    • Query-time SQL expressions as mapped attributes
  • Changing Attribute Behavior
    • Simple Validators
    • Using Custom Datatypes at the Core Level
    • Using Descriptors and Hybrids
    • Synonyms
    • Operator Customization
  • Composite Column Types
    • Tracking In-Place Mutations on Composites
    • Redefining Comparison Operations for Composites
    • Nesting Composites
• Mapping Class Inheritance Hierarchies
  • Joined Table Inheritance
    • Relationships with Joined Inheritance
    • Loading Joined Inheritance Mappings
  • Single Table Inheritance
    • Resolving Column Conflicts
    • Relationships with Single Table Inheritance
    • Loading Single Inheritance Mappings
  • Concrete Table Inheritance
    • Concrete Polymorphic Loading Configuration
    • Abstract Concrete Classes
    • Classical and Semi-Classical Concrete Polymorphic Configuration
    • Relationships with Concrete Inheritance
    • Loading Concrete Inheritance Mappings
• Non-Traditional Mappings
  • Mapping a Class against Multiple Tables
  • Mapping a Class against Arbitrary Subqueries
  • Multiple Mappers for One Class
• Configuring a Version Counter
  • Simple Version Counting
  • Custom Version Counters / Types
  • Server Side Version Counters
  • Programmatic or Conditional Version Counters
• Class Mapping API