Open-source Microsoft SQL Server alternatives

PostgreSQL is a feature-rich object-relational database management system covering a large part of the SQL standard. Its feature set includes transactions, foreign keys, subqueries, triggers, and user-defined types and functions, and the distribution also contains C language bindings. This GitHub repository is only a mirror of the official git repository, written in C, and the metadata lists the license as Other.

The project does not use GitHub pull requests; contributors submit patches through the process described on the PostgreSQL wiki. Copyright and license terms are in the COPYRIGHT file, general documentation for each version is published on the project site, and build instructions explain how to compile the server from source. The latest releases of the software and related software are available from the PostgreSQL website. Many hosting providers offer managed PostgreSQL, but the project itself is software you install and operate.

MySQL is a widely used open-source relational database. This repository contains the MySQL Server source code along with MySQL Cluster, which the description presents as a real-time, open-source transactional database. Applications talk to it using SQL, and it is a common choice for web applications and embedded products.

The MySQL website describes several offerings built around the server: the Community Edition, with a published governance model and early access builds; MySQL Enterprise Edition for advanced features, management tools and technical support; MySQL HeatWave, a cloud service that combines transactions with analytics and machine learning; and MySQL Cluster CGE. A program for OEM and ISV vendors covers embedding the database in other products.

The server is written in C++ and distributed under licenses detailed in the repository. Organizations can run the Community Edition on their own infrastructure, buy a commercial edition from Oracle, which owns the project, or use a managed cloud offering. Documentation, downloads and a developer zone are available on mysql.com.

MariaDB Server is an open-source relational database built by a global community with the MariaDB Foundation and MariaDB plc. It started out as a MySQL fork driven by the people who created MySQL, keeps a high degree of MySQL compatibility, and is described as a straightforward migration target for existing MySQL deployments.

Since then it has gained its own capabilities. A native VECTOR data type with approximate nearest-neighbour HNSW indexing has been available since version 11.8. Pluggable storage engines include InnoDB, Aria and MyRocks, plus ColumnStore (analytics), Spider (sharding) and S3 (archiving). Replication options include async, semi-sync and parallel modes using global transaction IDs, and Galera provides synchronous multi-primary clustering. On the SQL side it offers common table expressions, window functions, temporal tables with system versioning, sequences and a range of JSON functions.

It also offers an Oracle SQL mode with PL/SQL-style routines, GIS data types and full-text indexing, and security features such as role-based access control, pluggable authentication, data-at-rest encryption and TLS. MariaDB is written in C++ and licensed under GPL-2.0, and you run it on your own servers or in the cloud.