PostgreSQL
/'post-gres-kyu-el/ An enhancement of the POSTGRES database system.
PostgreSQL is an advanced relational database management system with some object oriented approaches. PostgreSQL is developed and distributed as free software, and while retaining its freedom it remains technically and featurewise a worthy competitor to even the most advanced commercial alternatives.
It was also one of the first databases to offer MVCC as opposed to row-level locking or table locking, thereby greatly improving multi-user performance.
PostgreSQL implements an extended subset of ANSI SQL and runs on many platforms. It also has interfaces to many different programming languages and database protocols, like ODBC and JDBC.