< database , theory > A family of algebra with a well-founded semantics used for modelling the data stored in relational databases , and defining queries on it. The main operations of the relational algebra are the set operations (such as union , intersection , and cartesian product ), selection (keeping only some lines of a table ) and the projection (keeping only some columns).
The relational data model describes how the data is structured.
Codd's reduction algorithm can convert from relational calculus to relational algebra .
(1997-02-17)