July 2008
Intermediate to advanced
230 pages
4h 33m
English
Content preview from The Relational Database Dictionary, Extended Edition
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Chapter 11. J
JD Join dependency.
JD implied by superkeys The JD
Example: Let relvar R have attributes A, B, C, D, E, and F (only), and let it have keys {A}, {B}, and {C} (only). Let ABD denote the set of attributes {A,B,D}, and similarly for other letter combinations. Then the first of the following JDs is implied by the superkeys of R but the second and third aren't:
{ ABD, BCE, CF }{ ABD, CE, CF } { ABD, BCE, DF }
Note that relvar R necessarily ...
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