作者shadow216308 (无名shadow216308)
看板TransCSI
标题[问题] 资料库系统
时间Sat Dec 22 15:36:17 2007
谢谢聪明人的教导> <
1. what is a functional dependency ?
what are the possible sources of the information echame?
2.what undesirable dependencies are avoided when a relation is 2NF?
3.consider a relation R(A.B.C.D.E) with the following dependencies;
AB->C,CD->E,DE->B
is AB a condidata key of this relation ? if not, is ABD? Explain your answer
请中文解答就可以了> <
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