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. Relvar is not universally accepted as a term, and it certainly has no meaning in the context of existing database management system products that support SQL.
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. 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 because in SQL there are no variables, nor are there assignment operators.
References
C.J. Date, An Introduction to Database Systems, 8th Ed., pp. 65–6.
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