PostgreSQL is the most powerful open-source object-relational database system, maintained by a global developer community, renowned for its extensibility, standard compliance, and reliability.
MySQL is the world's most popular open-source relational database management system, originally developed by Sweden's MySQL AB in 1995 and now owned and maintained by Oracle Corporation, widely used by millions of websites and applications.
MariaDB is an open-source database fork of MySQL created by MySQL original founder Michael "Monty" Widenius, maintained by MariaDB Corporation Ab (Helsinki, Finland).