謝謝聰明人的教導> <
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
請中文解答就可以了> <
--
無名﹡http://www.wretch.cc/album/shadow216308
--
※ 發信站: 批踢踢實業坊(ptt.cc)
◆ From: 218.168.217.21