mysql - 如何计算 SQL 查询的选择谓词的否定？

Question

我有一个 sql 查询“q”，其形式为:

Select attribute from table1, table2 where  SC;

这里“SC”是q中所有选择谓词的合取

就我而言:SC is balance <1000 and salary >=50000

现在我想计算“NSC”，它是q中SC的否定，需要一些帮助。

Answer 1

根据您的帖子，您说i want to calculate "NSC" which is negation of SC和 SC是balance <1000 and salary >=50000

因此，SC 的否定就是 balance >= 1000 and salary < 50000

所以，你可以这样做

Select attribute from table1 where balance >= 1000 and salary < 50000

(或)

Select attribute from table1 
where attribute not in 
( select attribute from table1 
where balance <1000 and salary >=50000 )