問題詳情
41、Which of the following descriptions about key are not correct?
(A) Primary key must be a composite key and cannot be a simple key.
(B) Superkey, candidate key and primary key can all uniquely identify any given entity (row).
(C) Primary key is not a minimal superkey.
(D) There might be more than one candidate key in a relation.
參考答案
答案：A,C
難度：非常困難0
統計：A(0),B(0),C(0),D(0),E(0)