A.the same number of attributes,where each pair of corresponding attributes shares the same domain

A.实体完整性、参照完整性、用户自定义完整性

A.系统分析员

A.只能有一个

A.an attribute or a set of attributes with a unique value for each tuple of a relation

A.前后顺序能任意颠倒，一定要按照输入的顺序排列