PostgreSQL is an object-relational database management system (ORDBMS) based on POSTGRES, Version 4.2, developed at the University of California at Berkeley Computer Science Department. POSTGRES pioneered many concepts that only became available in some commercial database systems much later.
PostgreSQL is an open-source descendant of this original Berkeley code. It supports SQL92 and SQL99 and offers many modern features:
- complex queries
- foreign keys
- transactional integrity
- multiversion concurrency control
Additionally, PostgreSQL can be extended by the user in many ways, for example by adding new
- data types
- aggregate functions
- index methods
- procedural languages
And because of the liberal license, PostgreSQL can be used, modified, and distributed by everyone free of charge for any purpose, be it private, commercial, or academic.