Chapter 1. Introduction to PostgreSQL and SQL

PostgreSQL is an open source, client/server, relational database. PostgreSQL offers a unique mix of features that compare well to the major commercial databases such as Sybase, Oracle, and DB2. One of the major advantages to PostgreSQL is that it is open source?you can see the source code for PostgreSQL. PostgreSQL is not owned by any single company. It is developed, maintained, broken, and fixed by a group of volunteer developers around the world. You don't have to buy PostgreSQL?it's free. You won't have to pay any maintenance fees (although you can certainly find commercial sources for technical support).

PostgreSQL offers all the usual features of a relational database plus quite a few unique features. PostgreSQL offers inheritance (for you object-oriented readers). You can add your own data types to PostgreSQL. (I know?some of you are probably thinking that you can do that in your favorite database.) Most database systems allow you to give a new name to an existing type. Some systems allow you to define composite types. With PostgreSQL, you can add new fundamental data types. PostgreSQL includes support for geometric data types such as point, line segment, box, polygon, and circle. PostgreSQL uses indexing structures that make geometric data types fast. PostgreSQL can be extended?you can build new functions, new operators, and new data types in the language of your choice. PostgreSQL is built around client/server architecture. You can build client applications in a number of different languages, including C, C++, Java, Python, Perl, TCL/Tk, and others. On the server side, PostgreSQL sports a powerful procedural language, PL/pgSQL (okay, the language is sportier than the name). You can add procedural languages to the server. You will find procedural languages supporting Perl, TCL/Tk, and even the bash shell.