The relational model for database management:
based on Mathematical Set Theory and first formulated and proposed in 1969 by E.F. Codd.
In the relational model of a database, all data is represented in terms of:
grouped into relation (table).
The purpose of the relational model is to provide a declarative method for specifying data and queries:
IBM's original implementation of Codd's ideas was System R.
There have been several commercial and open source products based on Codd's ideas, including:
Most of these use the SQL data definition and query language.
In an SQL database schema:
However, it must be noted that SQL databases, including DB2, deviate from the relational model in many details. Codd fiercely argued against deviations that compromise the original principles.
The relational database implements this kind of features (non-exhaustive)