A family of algebra with a well-foundedsemantics 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)
