PostgreSQL Definition PostgreSQL (pronounced "post-gress-Q-L") is an open source relational database management system ( DBMS ) developed by a worldwide team of volunteers. PostgreSQL is not controlled by any corporation or other private entity and the source code is available free of charge. PostgreSQL supports transactions, subselects, trigger s, view s, foreign key referential integrity, and sophisticated locking. It runs on numerous platforms including Linux , most flavors of UNIX, M...