关系的完整性约束不包含( )。
- A.实体完整性
- B.参照完整性
- C.属性完整性
- D.用户定义完整性
正确答案及解析
正确答案
解析
完整性约束：防止的是对数据的意外破环。
实体完整性：规定基本关系R的主属性A不能取空。
用户自定义完整性：就是针对某一具体关系数据库的约束条件，反映某一具体应用所涉及的数据必须满足的语义要求，由应用的环境决定。如：年龄必须为大于0小于150的整数。
参照完整性/引用完整性：规定，若F是基本关系R的外码，它与基本关系S的主码K，相对应（基本关系R和S不一定是不同的关系），则R中每个元组在F上的值必须为：或者取空值；或者等于S中某个元组的主码值。
本题中属性完整性约束不属于关系的完整性约束。
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