Relvar

Relvar

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 R/M E. F. Codd regarding the same concept, and is not universally accepted as a term, and certainly has no meaning in context of existing DBMS products that support SQL.

The term is used in the well-known database textbook by C.J. Date to differentiate between a variable that contains a relation and the relation itself. However, quoting from that book, "we should warn you that the term "relvar" is not in common usage". Other database textbooks use the term relation (or table) for both the variable and the data it contains. This is most likely due to the fact that there are no variables, nor are there assignment operators -- fundamentally related to the concept of an explicit variable, in SQL.

Reference

C.J. Date, "An Introduction to Database Systems", 8th Ed., pp 65-66.


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