PostgreSQL

PostgreSQL is an advanced object-relational database management system. It stores and queries structured data using an extended subset of the SQL standard, with transactions, foreign keys, subqueries, triggers, user-defined types, and user-defined functions.

Because types and functions are user-extensible, you can model domain-specific data inside the database rather than working around a fixed schema. C language bindings let applications talk to the server directly, and the system runs as a self-hosted server on a wide range of operating systems.

PostgreSQL is released under its own permissive license and developed by the PostgreSQL Global Development Group. It is widely used as a general-purpose relational backend for everything from small applications to large production systems.