1. What Is PostgreSQL™?
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## 1. What Is PostgreSQL™? #

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 a large part of the SQL standard and offers many modern features:

- complex queries
- foreign keys
- triggers
- updatable views
- transactional integrity
- multiversion concurrency control

Also, PostgreSQL™ can be extended by the user in many ways, for example by adding new

- data types
- functions
- operators
- aggregate functions
- index methods
- procedural languages

And because of the liberal license, PostgreSQL™ can be used, modified, and distributed by anyone free of charge for any purpose, be it private, commercial, or academic.

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