問題詳情
20、 Which of the following descriptions about secondary key is not correct?
(A)Secondary key is not necessary unique.
(B) Secondary key cannot be a foreign key.
(C) Secondary key is used for data retrieval purpose.
(D)Secondary key can be a single attribute.
參考答案
答案：B
難度：困難0.375
統計：A(3),B(3),C(1),D(1),E(0)