使用SELECT删除(错误1093)

Question

我需要删除这个查询中的结果：

SELECT a.cad_id
FROM `Cad` a
WHERE NOT EXISTS
(
SELECT b.cad_id
FROM `rel` b
WHERE a.cad_id = b.rel
)

我试着：

DELETE FROM `Cad` WHERE cad_id = (
SELECT a.cad_id
FROM `Cad` a
WHERE NOT EXISTS
(
SELECT b.cad_id
FROM `rel` b
WHERE a.cad_id = b.rel
)
)

1093 -不能指定目标表'Cad‘以便在FROM子句中更新

我该怎么解决呢？

Answer 1

在临时表中选择内部查询数据。

DELETE FROM `cad` 
WHERE  cad_id IN (SELECT * 
                 FROM  (SELECT a.cad_id 
                        FROM   `cad` a 
                        WHERE  NOT EXISTS (SELECT b.cad_id 
                                           FROM   `rel` b 
                                           WHERE  a.cad_id = b.rel)) AS 
                       tempTable)