1

我可以做这个:

SELECT t2.value + sum(t3.value)
FROM tableA t2, tableB t3
WHERE t2.somekey = t3.somekey
GROUP BY t3.somekey

但是如何做到这一点?

 UPDATE tableA t1
    SET speed = (
        SELECT t2.value + sum(t3.value)
        FROM tableA t2, tableB t3
        WHERE t2.somekey = t3.somekey
        AND t1.somekey = t3.somekey
        GROUP BY t3.somekey
   )
;

MySQL 说这是非法的,因为您不能t1在 FROM 子句中指定要更新的目标表。

4

2 回答 2

8

您可以通过重写查询来做到这一点:

UPDATE tableA t1, (
   SELECT somekey, SUM(value) value
   FROM tableB t3
   GROUP BY somekey
) t2
SET speed = t1.value + t2.value
WHERE t1.somekey = t2.somekey;
于 2010-05-04T13:56:40.627 回答
-1

您正在使用不应在此上下文中使用MySQL的扩展名。GROUP BY

给定以下值:

tableA

value somekey
1     1
2     1

tableB

value somekey
3     1
4     1

这个子查询:

    SELECT  t2.value + SUM(t3.value)
    FROM    tableA t2, tableB t3
    WHERE   t2.somekey = t3.somekey
            AND t1.somekey = t3.somekey
    GROUP BY
            t3.somekey

将返回8或返回9:它将计算SUM(b.value) = 7然后为给定键添加一个随机值。A

对于此示例数据,您希望将速度更新到哪个值?

于 2010-05-04T13:51:15.640 回答