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The Relational Database Dictionary, Extended Edition by C. J. Date

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Chapter 19. R

range 1. See function. 2. See range variable.

range variable Relational calculus analog of a logic variable; in other words, a variable that "ranges over" some specified set of valueseither the set of tuples in some relation (in tuple calculus) or the set of values of some type (in domain calculus)and can appear either bound or free in relational calculus expressions.

Examples: See the examples under domain calculus and tuple calculus.

RANK See ranking.

ranking Let r be a relation with no attribute called X. Then the ranking RANK r BY (item, . . ., item AS X), where each item consists of either ASC (ascending) or DESC (descending) followed by an attribute reference identifying an attribute of r (and the overall sequence of items specifies ...

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