假设关系 R(A1,A2,A3)上的一个分解为ρ={(A1,A2),(A1,A3)}，下表是关系 R 上的一个实例，根据实例推出 R 的函数依赖集 F 为（请作答此空），分解 p（ ）。
- A.是无损联接的
- B.是保持函数依赖的
- C.是有损联接的
- D.无法确定是否保持函数依赖
正确答案及解析
正确答案
解析
A1是a，A2可以是a或b或c，无法确定唯一字符，但是A1A3的组合可以唯一确定A2，A1A2的组合同理。判断是否为无损连接，首先进行(A1A2)∩(A1A3)=A1，因为A1无法唯一确定A2、A3，因此该分解为有损连接。
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