Relational databases were first defined in June 1970 by Edgar Codd at IBM's San Jose Research Laboratory. [1] Codd's views on RDBMSs are summarized in Codd's 12 Rules. Relational databases have become the dominant database type. Other models besides the relational model include the hierarchical database model and the network model.

The following table summarizes some of the most important relational database terms and corresponding SQL terms:

In a relational database, a relation is a set of tuples with the same properties. A tuple typically represents an object and information about that object. Objects are usually physical objects or concepts. A relation is usually described as a table, which is organized into rows and columns. All data referenced by an attribute are in the same domain and conform to the same constraints.

They are often used as application programming interfaces (APIs) for security or simplicity. Implementations of stored procedures on SQL RDBMSs typically allow developers to take advantage of (often vendor-specific) procedural extensions to the standard declarative SQL syntax. Stored procedures are not part of the relational database model, but all commercial implementations include them.