Oracle database is a relational database management system (RDBMS) from Oracle Corporation, which runs on more than 80 platforms. Introduced in the late 1970s, Oracle was the first database product to run on a variety of platforms from micro to mainframe. The Oracle database is Oracle's flagship product, and version 11g was introduced in 2007.

SQL Server is a relational database management system (RDBMS) from Microsoft that's designed for the enterprise environment. SQL Server runs on T-SQL (Transact -SQL), a set of programming extensions from Sybase and Microsoft that add several features to standard SQL, including transaction control, exception and error handling, row processing, and declared variables. SQL Server 2005 was released in November 2005.

DB2 is a family of relational database management system (RDBMS) products from IBM that serve a number of different operating system platforms. Although DB2 products are offered for Unix-based systems and personal computer operating systems, DB2 trails Oracle's database products in UNIX-based systems and Microsoft's Access in Windows systems.

MySQL is a relational database management system (RDBMS) based on SQL (Structured Query Language). First released in January, 1998, MySQL is now one component of parent company MySQL AB's product line of database servers and development tools. MySQL is open source software and free to use. MySQL runs on virtually all platforms, including Linux, Unix, and Windows; and is widely used for web applications and embedded applications.

Microsoft Access is a relational database management system (RDBMS) from Microsoft that combines the relational Microsoft Jet Database Engine with a graphical user interface and software development tools. Access is used by small businesses, within departments of large corporations, and by hobby programmers to create ad hoc customized desktop systems for handling the creation and manipulation of data. Access can be used as a database only for basic web based applications.