SQL删除行只有一组列的所有值都等于

Question

考虑两个表

表一：

Fields : 
- a_ID1 
- a_Status  
- a_Key 

表B：

Fields : 
- b_ID 
- b_Status 
- FK_a_key 

有没有办法删除来自两个表的一组行关于以下条件：
删除每一行，其中FK_a_key = xxx and a_key = xxx 但仅当非这行的e的状态字段与“2”不同？

Answer 1

一对夫妇的not exists调用应该做的伎俩：

DELETE FROM a 
WHERE a_key = 'xxx' AND 
     NOT EXISTS (SELECT * 
        FROM a 
        WHERE a_key = 'xxx' AND a_status != 2) AND 
     NOT EXISTS (SELECT * 
        FROM b 
        WHERE FK_a_key = 'xxx' AND b_status != 2) 


DELETE FROM b 
WHERE b_key = 'xxx' AND 
     -- Frankly, both these conditions are are redundant - 
     -- they've been checked in the previous statement 
     NOT EXISTS (SELECT * 
        FROM a 
        WHERE a_key = 'xxx' AND a_status != 2) AND 
     NOT EXISTS (SELECT * 
        FROM b 
        WHERE FK_a_key = 'xxx' AND b_status != 2)