MySQL | 您不能在FROM子句中指定目标表“ a”进行更新

Question

DELETE FROM table_a WHERE id IN(
    SELECT table_a.id AS id FROM table_a, table_b 
    WHERE table_a.object_id = 1 AND table_a.code = 'code' 
        AND table_a.code = table_b.code 
        AND table_b.id = table_a.b_id 
        AND table_b.table = 'testTable')

这是我希望MySQL执行的（稍微简化了）查询。 我在stackoverflow的其他页面上读到，不支持此功能，并且可以通过使用JOINS来解决。 如何使用JOINS将其“转录”为查询？ 我发现这样做很困难，因为我从未尝试使用多个表创建DELETE查询。

Answer 1

您不能从表中删除并在子查询中引用同一表，这只是MySQL的限制。 类似于以下内容的东西应该起作用：

DELETE FROM table_a 
USING table_a
INNER JOIN table_b
    ON table_a.code = table_b.code
    AND table_b.id = table_a.b_id
    AND table_b.table = 'testTable'
WHERE table_a.object_id = 1 
    AND table_a.code = 'code' 

重要的是USING 。 如果仅将两个表连接在一起，则将从两个表中删除记录。 USING告诉MySQL使用这些表进行处理，但只能从FROM子句中的表中删除。

http://dev.mysql.com/doc/refman/5.0/en/delete.html

Answer 2

这是一个常见的MySQL问题，请在select和update / delete之间使用一个临时表：

DELETE FROM table_a WHERE id IN 
   (select id from 
       (SELECT table_a.id AS id FROM table_a, table_b 
        WHERE table_a.object_id = 1 
        AND table_a.code = 'code' 
        AND table_a.code = table_b.code 
        AND table_b.id = table_a.b_id 
        AND table_b.table = 'testTable')
    ) tempTable

Answer 3

从多重表中删除有两种（略有不同）语法。 这是一个没有USING ：

DELETE a
FROM 
      table_a AS a 
  INNER JOIN 
      table_b AS b
    ON  b.code = a.code
    AND b.id   = a.b_id   
WHERE 
      a.object_id = 1 
  AND a.code = 'code' 
  AND b.`table` = 'testTable'   --- Do you actually have a column named "table"?

Answer 4

我的方式...如果可以使用！

DELETE FROM table_a WHERE id IN(SELECT id FROM(SELECT id FROM table_a WHERE userid=99 GROUP BY mobile HAVING COUNT(mobile) > 1) as t2)