> For the complete documentation index, see [llms.txt](https://docs.postgresql.tw/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.postgresql.tw/preface/intro-whatis.md).

# 1. What Is PostgreSQL ? \#

PostgreSQL is an object-relational database management system (ORDBMS) based on [POSTGRES, Version 4.2](https://dsf.berkeley.edu/postgres.html), 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](/the-sql-language.md)
* [foreign keys](/the-sql-language/ddl/ddl-constraints.md#DDL-CONSTRAINTS-FK)
* [triggers](/server-programming/triggers.md)
* [updatable views](/reference/sql-commands/sql-createview.md#SQL-CREATEVIEW-UPDATABLE-VIEWS)
* [transactional integrity](/the-sql-language/mvcc/transaction-iso.md)
* [multiversion concurrency control](/the-sql-language/mvcc.md)

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

* [data types](/the-sql-language/datatype.md)
* [functions](/the-sql-language/functions.md)
* [operators](/the-sql-language/functions.md)
* [aggregate functions](/the-sql-language/functions/functions-aggregate.md)
* [index methods](/the-sql-language/indexes.md)
* [procedural languages](/server-programming.md)

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.

***

原文：[PostgreSQL 18.6 Documentation](https://www.postgresql.org/docs/18/intro-whatis.html)（英文原文，待翻譯）


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