Original author(s) Written in Python | Development status Active Operating system | |
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Initial release February 14, 2006; 11 years ago (2006-02-14) Stable release 1.1.6 / 28 February 2017; 26 days ago (2017-02-28) | ||
SQLAlchemy is an open source SQL toolkit and object-relational mapper (ORM) for the Python programming language released under the MIT License.
Contents
SQLAlchemy provides "a full suite of well known enterprise-level persistence patterns, designed for efficient and high-performing database access, adapted into a simple and Pythonic domain language". SQLAlchemy's philosophy is that SQL databases behave less and less like object collections the more size and performance start to matter, while object collections behave less and less like tables and rows the more abstraction starts to matter. For this reason it has adopted the data mapper pattern (like Hibernate for Java) rather than the active record pattern used by a number of other object-relational mappers. However, optional plugins allow users to develop using declarative syntax.
SQLAlchemy was first released in February 2006 and has quickly become one of the most widely used object-relational mapping tools in the Python community, alongside Django's ORM.
Example
The following example represents an n-to-1 relationship between movies and their directors. It is shown how user-defined Python classes create corresponding database tables, how instances with relationships are created from either side of the relationship, and finally how the data can be queried—illustrating automatically-generated SQL queries for both lazy and eager loading.
Schema definition
Creating two Python classes and according database tables in the DBMS:
Data insertion
One can insert a director-movie relationship via either entity:
Querying
SQLAlchemy issues the following query to the DBMS (omitting aliases):
The output:
Setting lazy=True (default) instead, SQLAlchemy would first issue a query to get the list of movies and only when needed (lazy) for each director a query to get the name of the according director: