PostgreSQL: Up and Running

PostgreSQL is an open source relational database management system that began as a University of California, Berkeley project. It was originally under the BSD license, but is now called the PostgreSQL License (TPL). For all intents and purposes, it’s BSD licensed. It has a long history, almost dating back to the beginning of relational databases.
It has enterprise class features such as SQL windowing functions, the ability to create
aggregate functions and also utilize them in window constructs, common table and
recursive common table expressions, and streaming replication. These features are
rarely found in other open source database platforms, but commonly found in newer
versions of the proprietary databases such as Oracle, SQL Server, and IBM DB2. What
sets it apart from other databases, including the proprietary ones we just mentioned,
is the ease with which you can extend it without changing the underlying base—and
in many cases, without any code compilation. Not only does it have advanced features,
but it performs them quickly. It can outperform many other databases, including proprietary
ones for many types of database workloads.