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function sqlalchemy.orm.relationship(argument: _RelationshipArgumentType[Any] | None = None, secondary: _RelationshipSecondaryArgument | None = None, *, uselist: bool | None = None, collection_class: Type[Collection[Any]] | Callable[[], Collection[Any]] | None = None, primaryjoin: _RelationshipJoinConditionArgument | None = None, secondaryjoin: _RelationshipJoinConditionArgument | None = None, bac

Performance¶ Why is my application slow after upgrading to 1.4 and/or 2.x?¶ SQLAlchemy as of version 1.4 includes a SQL compilation caching facility which will allow Core and ORM SQL constructs to cache their stringified form, along with other structural information used to fetch results from the statement, allowing the relatively expensive string compilation process to be skipped when another str

Basic Relationship Patterns¶ A quick walkthrough of the basic relational patterns, which in this section are illustrated using Declarative style mappings based on the use of the Mapped annotation type. The setup for each of the following sections is as follows: from __future__ import annotations from typing import List from sqlalchemy import ForeignKey from sqlalchemy import Integer from sqlalchem

We’ve Moved! This page is the previous home of the SQLAlchemy 1.x Tutorial. As of 2.0, SQLAlchemy presents a revised way of working and an all new tutorial that presents Core and ORM in an integrated fashion using all the latest usage patterns. See SQLAlchemy Unified Tutorial. © Copyright 2007-2025, the SQLAlchemy authors and contributors. flambé! the dragon and The Alchemist image designs created

We’ve Moved! This page is the previous home of the SQLAlchemy 1.x Tutorial. As of 2.0, SQLAlchemy presents a revised way of working and an all new tutorial that presents Core and ORM in an integrated fashion using all the latest usage patterns. See SQLAlchemy Unified Tutorial.

© Copyright 2007-2024, the SQLAlchemy authors and contributors. flambé! the dragon and The Alchemist image designs created and generously donated by Rotem Yaari. Created using Sphinx 7.2.6. Documentation last generated: Thu 31 Oct 2024 09:39:37 AM EDT Website content copyright © by SQLAlchemy authors and contributors. SQLAlchemy and its documentation are licensed under the MIT license. SQLAlchemy

The Type Hierarchy¶ SQLAlchemy provides abstractions for most common database data types, as well as several techniques for customization of datatypes. Database types are represented using Python classes, all of which ultimately extend from the base type class known as TypeEngine. There are two general categories of datatypes, each of which express themselves within the typing hierarchy in differe

ORM Examples¶ The SQLAlchemy distribution includes a variety of code examples illustrating a select set of patterns, some typical and some not so typical. All are runnable and can be found in the /examples directory of the distribution. Descriptions and source code for all can be found here. Additional SQLAlchemy examples, some user contributed, are available on the wiki at https://www.sqlalchemy.

Connection Pooling¶ A connection pool is a standard technique used to maintain long running connections in memory for efficient re-use, as well as to provide management for the total number of connections an application might use simultaneously. Particularly for server-side web applications, a connection pool is the standard way to maintain a “pool” of active database connections in memory which a

Working with Engines and Connections¶ This section details direct usage of the Engine, Connection, and related objects. Its important to note that when using the SQLAlchemy ORM, these objects are not generally accessed; instead, the Session object is used as the interface to the database. However, for applications that are built around direct usage of textual SQL statements and/or SQL expression c

© Copyright 2007-2025, the SQLAlchemy authors and contributors. flambé! the dragon and The Alchemist image designs created and generously donated by Rotem Yaari. Created using Sphinx 8.2.3. Documentation last generated: Sat 07 Jun 2025 09:31:34 AM EDT Website content copyright © by SQLAlchemy authors and contributors. SQLAlchemy and its documentation are licensed under the MIT license. SQLAlchemy

DBAPI Support¶ The following dialect/DBAPI options are available. Please refer to individual DBAPI sections for connect information. psycopg2 psycopg (a.k.a. psycopg 3) pg8000 asyncpg psycopg2cffi Sequences/SERIAL/IDENTITY¶ PostgreSQL supports sequences, and SQLAlchemy uses these as the default means of creating new primary key values for integer-based primary key columns. When creating tables, SQ

DBAPI Support¶ The following dialect/DBAPI options are available. Please refer to individual DBAPI sections for connect information. mysqlclient (maintained fork of MySQL-Python) PyMySQL MariaDB Connector/Python MySQL Connector/Python asyncmy aiomysql CyMySQL PyODBC Supported Versions and Features¶ SQLAlchemy supports MySQL starting with version 5.0.2 through modern releases, as well as all modern

New to SQLAlchemy? Start here: For Python Beginners: Installation Guide - basic guidance on installing with pip and similar For Python Veterans: SQLAlchemy Overview - brief architectural overview New users of SQLAlchemy, as well as veterans of older SQLAlchemy release series, should start with the SQLAlchemy Unified Tutorial, which covers everything an Alchemist needs to know when using the ORM or