※ 引述《shadow216308 (無名shadow216308)》之銘言：
: 2.what undesirable dependencies are avoided when a relation is 2NF?
partial functional dependency
意即所有非鍵值完全功能相依於主鍵
: 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
^^^^^^^^^
candidate
AB不是；ABD是
候選鍵有唯一性(可唯一識別所有值組)和最小性(不可縮減)
只有AB的話無法決定E，ABD即可完全識別
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