改进 mysql 查询

Question

我有一个疑问。

DELETE FROM A  
WHERE i NOT IN 
( SELECT i FROM B WHERE j = 1  
  UNION select i from C 
  UNION select i from D 
);

基本上删除 A 中字段 i 未出现在表 B、C 或 D 中的所有行。如果只是：

DELETE FROM A  
WHERE i NOT IN 
( SELECT i FROM B 
);

那么可以使用左连接轻松完成

DELETE A FROM A 
LEFT JOIN B 
ON A.i = B.i
WHERE B.id is NULL;

（假设每个表都有一个 id模式中的字段）

我想我的问题是上面的内容是否扩展到 三表场景有以下解决方案吗？

DELETE A FROM A 
LEFT JOIN B 
ON A.i = B.i AND B.j = 1
LEFT JOIN C
ON A.i = C.i 
LEFT JOIN D
ON A.i = D.i
WHERE B.id is NULL
AND   C.id is NULL
AND   D.id is NULL

Answer 1

像这样的事情：

DELETE 
  FROM A
 WHERE NOT EXISTS (
                   SELECT * 
                     FROM B
                    WHERE B.i = A.i
                  )
       AND NOT EXISTS (
                       SELECT * 
                         FROM C
                        WHERE C.i = A.i
                      )
       AND NOT EXISTS (
                       SELECT * 
                         FROM D
                        WHERE D.i = A.i
                      );