The other major player in the database game, Oracle, has been available under a proprietary license since it was released as Oracle V2 in 1979. It has undergone a number of major revisions since then and, in 2007, was released as Oracle 11g. Like DB2 and Informix, Oracle is mostly used for very large databases, such as those of global chain stores, technology companies, governments, and so forth. Because of the similar client bases enjoyed by IBM and Oracle, the companies tend to be mutually cooperative in database and middleware application development.

Microsoft SQL Server, initially based on Sybase, is another full-featured and expensive database system designed to attract large customers. Its primary competitors are IBM and Oracle, but Microsoft has, to a great extent, been unable to secure a significant percentage of the high-end database market as its client base. As a result, SQL Server caters mainly to the lower end of the pool of larger database customers.

Some speculate Microsoft’s inability to capture the higher end of the market is a result of SQL Server’s dependence on the Microsoft Windows operating system. In many cases, Windows is seen as less reliable and less stable than UNIX-based operating systems like Solaris, FreeBSD, and Linux; all of which support databases like Oracle, DB2 and Informix, and MySQL and PostgreSQL.

In order of market share in terms of net revenue in 2006, the leaders in database platform providers are Oracle, with the greatest market share; IBM; and Microsoft.

While the database systems with the greatest markets shares use SQL as their query language, other languages are used to interact with a handful of other relatively popular databases. Most developers will never encounter these languages in their daily work, but for purposes of being complete, some of these languages are IBM Business System 12, EJB-QL, Quel, Object Query Language, LINQ, SQLf, FSQL, and Datalog. Of particular note is IBM Business System 12, which preceded SQL but was, for some time, used with System R instead of SQL due to SQL being relationally incomplete at the time.

Today, organizations with large database projects tend to choose Oracle, DB2, Informix, Sybase, or Microsoft SQL Server for their database platforms because of the comprehensive support contracts offered in conjunction with those products. Smaller organizations or organizations with technology-heavy staff might choose PostgreSQL or MySQL because they are free and offer good, community-based support.

Terminology

The term “database” is widely misused to refer to an entire database system. Oracle, for example, is not a database but a full-featured Database Management System (DBMS). In fact, a DBMS can be used to manage many databases, and as such, a database is just one part of a DBMS. In this series of articles, the terms “database system” and “database platform” are used to refer to the idea of a DBMS.

Further, most modern database systems employ the idea of the relational database, and they are properly called Relational Database Management Systems (RDBMS). The distinction between a DBMS and a RDBMS, unless critical to the understanding of a specific topic, is not made in these articles.