Question

我有这个简单的SQL问题。

UPDATE parts
SET partscnt=partscnt-1
WHERE idparts = (SELECT idparts FROM ordercontent WHERE idOrder=4);

问题是子查询返回5个值，我希望对每个值进行更新。

更新： ordercontent表具有订单的ID和行idparts。如果几个相同的部分挂钩到相同的顺序，表格如下所示：

ID idparts
4  147
4  147
4  147
4  55
4  33

所以我需要为id为147的部分减少partscount三次。

如何更改此查询以实现该目标？

Answer 1

尝试一下：

UPDATE parts 
SET partscnt = partscnt-1 
WHERE idparts IN (
    SELECT idparts 
    FROM ordercontent 
    WHERE idOrder = 4
);

Answer 2

查找指定订单的idparts中每个ordercontent的数量：

SELECT idparts,
       COUNT(*) AS cnt
FROM ordercontent
WHERE idOrder = 4
GROUP BY idparts

将上述结果加入parts并使用cnt值更新partscnt：

UPDATE parts p
INNER JOIN (
    SELECT idparts,
           COUNT(*) AS cnt
    FROM ordercontent
    WHERE idOrder = 4
    GROUP BY idparts
) o
ON p.idparts = o.idparts
SET p.partscnt = p.partscnt - o.cnt
;

Answer 3

用IN：

替换'='

UPDATE parts SET partscnt = partscnt-1 WHERE idparts IN （SELECT idparts FROM ordercontent WHERE idOrder = 4）;

Answer 4

UPDATE parts 
SET partscnt=partscnt-1 
WHERE idparts IN
    (SELECT idparts FROM ordercontent WHERE idOrder=4);

Answer 5

UPDATE parts p1
INNER JOIN 
(
   SELECT *  
   FROM ordercontent WHERE idOrder = 4
) p2 ON p1.idparts = p2.idparts
SET p1.partscnt = p2.partscnt-1

Answer 6

将“-1”替换为“（SELECT COUNT（*）FROM ordercontent WHERE isOrder = 4）”

根据返回多行的子查询更新值

6 个答案: