Relationship Configuration

This section describes the relationship() function and in depth discussion of its usage. For an introduction to relationships, start with Working with ORM Related Objects in the SQLAlchemy Unified Tutorial.

• Basic Relationship Patterns
  • Declarative vs. Imperative Forms
  • One To Many
    • Using Sets, Lists, or other Collection Types for One To Many
    • Configuring Delete Behavior for One to Many
  • Many To One
    • Nullable Many-to-One
  • One To One
    • Setting uselist=False for non-annotated configurations
  • Many To Many
    • Setting Bi-Directional Many-to-many
    • Using a late-evaluated form for the “secondary” argument
    • Using Sets, Lists, or other Collection Types for Many To Many
    • Deleting Rows from the Many to Many Table
  • Association Object
    • Combining Association Object with Many-to-Many Access Patterns
  • Late-Evaluation of Relationship Arguments
    • Adding Relationships to Mapped Classes After Declaration
    • Using a late-evaluated form for the “secondary” argument of many-to-many
• Adjacency List Relationships
  • Composite Adjacency Lists
  • Self-Referential Query Strategies
  • Configuring Self-Referential Eager Loading
• Configuring how Relationship Joins
  • Handling Multiple Join Paths
  • Specifying Alternate Join Conditions
  • Creating Custom Foreign Conditions
  • Using custom operators in join conditions
  • Custom operators based on SQL functions
  • Overlapping Foreign Keys
  • Non-relational Comparisons / Materialized Path
  • Self-Referential Many-to-Many Relationship
  • Composite “Secondary” Joins
  • Relationship to Aliased Class
    • Using the AliasedClass target in Queries
  • Row-Limited Relationships with Window Functions
  • Building Query-Enabled Properties
• Working with Large Collections
  • Write Only Relationships
    • Creating and Persisting New Write Only Collections
    • Adding New Items to an Existing Collection
    • Querying Items
    • Removing Items
    • Bulk INSERT of New Items
    • Bulk UPDATE and DELETE of Items
    • Write Only Collections - API Documentation
  • Dynamic Relationship Loaders
    • Dynamic Relationship Loaders - API
  • Setting RaiseLoad
  • Using Passive Deletes
• Collection Customization and API Details
  • Customizing Collection Access
    • Dictionary Collections
  • Custom Collection Implementations
    • Annotating Custom Collections via Decorators
    • Custom Dictionary-Based Collections
    • Instrumentation and Custom Types
  • Collection API
    • attribute_keyed_dict()
    • column_keyed_dict()
    • keyfunc_mapping()
    • attribute_mapped_collection
    • column_mapped_collection
    • mapped_collection
    • KeyFuncDict
    • MappedCollection
  • Collection Internals
    • bulk_replace()
    • collection
    • collection_adapter
    • CollectionAdapter
    • InstrumentedDict
    • InstrumentedList
    • InstrumentedSet
    • prepare_instrumentation()
• Special Relationship Persistence Patterns
  • Rows that point to themselves / Mutually Dependent Rows
  • Mutable Primary Keys / Update Cascades
    • Simulating limited ON UPDATE CASCADE without foreign key support
• Using the legacy ‘backref’ relationship parameter
  • Backref Default Arguments
  • Specifying Backref Arguments
• Relationships API
  • relationship()
  • backref()
  • dynamic_loader()
  • foreign()
  • remote()