Why ___ she ___ tigers?[ ]
A. is, like
B. does, likes
C. does, like
D. don't like
答案:C
关系中的“主码”不允许取空值是指______约束规则。
A.实体完整性
B.引用完整性
C.用户定义的完整性
D.数据完整性
消毒概述