High Quality Content by WIKIPEDIA articles! In relational databases, a relvar is a term coined by C. J. Date as an abbreviation for the concept of relation variable, which is the actual term used by the inventor of the relational model, E. F. Codd, regarding the same concept. The term is used in Date`s well-known database textbook An Introduction to Database Systems to differentiate between a variable that contains a relation and the relation itself.