August 2009
Intermediate to advanced
893 pages
26h 48m
English
Content preview from Database Systems: Concepts, Design and Applications
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4.5. Relational Calculus
Tuple and domain calculi are collectively referred to as relational calculus. Relational calculus is a query system wherein queries are expressed as formulas consisting of a number of variables and an expression involving these variables. Such formulas describe the properties of the required result relation without specifying the method of evaluating it. Thus, in a relational calculus, there is no description of how to evaluate a query; a relational calculus query specifies what is to be retrieved rather than how to retrieve it. It is up to the DBMS to transform these nonprocedural queries into equivalent and efficient procedural queries.
A relational calculus has nothing to do with differentiation or integration of ...