A '''relationalRelational databaseDatabase managementManagement systemSystem (RDBMS)''' is a [[database management system]] (DBMS) that is based on the [[relational model]] as introduced by [[Edgar F. Codd]]. Strictly speaking it should also satisfy [[Codd's 12 rules]], but in practice there is no DBMS that satisfies all these rules. In fact, most successful DBMSs (and the query language [[SQL]])DBMS that are considered to be relational violate the relational model in several important ways, including the [[Structured Query Language]] (SQL). However, most database practitioners and researchers use the term in a loose way such that most databases that support SQL are also included.
The first released RDBMS —that was a relatively faithful implementation of the relational model— was the [[Multics Relational Data Store]],; first sold in [[1978]]. Others have been [[Berkeley Ingres QUEL]] and [[IBM BS12]].
Today, popular commercial RDBMS's for large databases include [[Oracle database|Oracle]], [[Microsoft SQL Server]], [[Sybase SQL Server]], and IBM's [[DB2]]. The most commonly used free RDBMS's are [[MySQL]], [[PostgreSQL]] and [[Firebird (database server)|Firebird]].
=== External links ===
* "''[http://www.dbdebunk.com Database Debunkings]''" ** :Critic point of view that argues that it is important that the predicate ''relational'' should be reserved for those DBMSsDBMS that are fully faithful to the relational model. However, this is not common practice.
