PostgreSQL, first developed in 1977 as the Ingres database by the University of California at Berkeley, is an open source, object-relational database management system. It is arguably the most capable of all the open source databases. This text provides a guide to installation, configuration and usage. It shows how to compile PostgreSQL from source, create a database and configure PostgreSQL to accept client-server connections. The book also delves into the application's many advanced features, such as support for transactions, versioning, replication, and various referential integrity features. PostgreSQL's PL/pgSQL programming language, a very useful but under-documented feature, is introduced explaining how it can be used to develop stored procedures and triggers. The book inclues a command reference.