Open Source Databases Comparison: MySQL, PostSQL and mSQL - page 2
All the products mentioned above have a number of common features: They use a subset of the features of ANSI SQL. This allows a program or user to store, manipulate and retrieve data in table structures. They all have a sophisticated and flexible client server architecture. The backend on all these programs (the part that does the work) is a standalone application that listens for connections on a well known TCP port. All include debugging and monitoring tools for writing software applications and tracing problems and all support a number of programming languages.