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Introduction
TYPO3 relies on storing its data in a relational database management system (RDBMS). The Doctrine DBAL component is used to enable connecting to different database management systems. Most used is still MySQL / MariaDB, but thanks to Doctrine others like PostgreSQL and SQLServer are also an option.
The corresponding DBMS can be selected during installation.
Note
At the time of writing the installation process does not fully work for SQL Server, the connection settings have to be manually configured in that case.
This chapter gives an overview of the basic TYPO3 database table structure, followed by some information on upgrading and maintaining table and field consistency, and then deep dives into the programming API.
Doctrine DBAL
Database queries in TYPO3 are done with an API based on Doctrine DBAL.
The API is provided by the system extension core, which is always loaded and
thus always available.
Extension authors can use this low-level API to manage query operations directly on the configured DBMS.
Doctrine DBAL is rich in features. Drivers for various target systems enable TYPO3 to run on a long list of ANSI SQL-compatible DBMSes. If used properly, queries created with this API are translated to the specific database engine by Doctrine without an extension developer taking care of that specifically.
The API provided by the Core is basically a pretty small and lightweight facade in front of Doctrine DBAL that adds some convenient methods as well as some TYPO3-specific sugar. The facade additionally provides methods to retrieve specific connection objects per configured database connection based on the table that is queried. This enables instance administrators to configure different database engines for different tables, while being transparent to extension developers.
This document does not outline every single method that the API provides. It sticks to those that are commonly used in extensions, and some parts like the rewritten schema migrator are omitted as they are usually of little to no interest to extensions.
Understanding Doctrine DBAL and Doctrine ORM
Doctrine is a two-part project, with Doctrine DBAL being the low-level database abstraction and the interface for building queries to specific database engines, while Doctrine ORM is a high-level object relational mapping on top of Doctrine DBAL.
The TYPO3 Core implements - only - the DBAL part. Doctrine ORM is neither required nor implemented nor used.
Low-level and high-level database calls
This documentation focuses on low-level database calls. In many cases, it is better to use higher level APIs such as the DataHandler or Extbase repositories and to let the framework handle persistence details internally.
Tip
Always remember the high-level database calls and use them when appropriate!
Credits
Implementing the Doctrine DBAL API into TYPO3 has been a huge project in
2016. Special thanks goes to awesome Mr. Morton Jonuschat for the initial
design, integration and support and to more than 40 different people who
actively contributed to migrate more than 1700 calls from TYPO3_DB-style to
Doctrine within half a year.
This was a huge community achievement, thanks everyone involved!