Question

UPDATE table1 AS t1 
       INNER JOIN table2 AS t2 ON t1.table1_id=t2.table2_id 
   SET t1.overview=t2.val 
 WHERE t1.table1_id=(SELECT table2_id
                       FROM table2
                      WHERE table2_id=1);

table2有多个id值为1，因此它给出了

#1242 - Subquery returns more than 1 row

Answer 1

您需要DISTINCT。

UPDATE table1 AS t1
INNER JOIN table2 AS t2
ON t1.table1_id = t2.table2_id
SET t1.overview = t2.val
WHERE t1.table1_id = (SELECT DISTINCT table2_id FROM table2 WHERE table2_id = 1);

如果table2_id已修复，为什么不要像以下那样使用1：

UPDATE table1 AS t1
INNER JOIN table2 AS t2
ON t1.table1_id = t2.table2_id
SET t1.overview = t2.val
WHERE t1.table1_id = 1;

Answer 2

如果您确实想将t1.table1_id与多个值进行比较，请使用：

中的

而不是 =

UPDATE table1 AS t1 INNER JOIN table2 AS t2 ON t1.table1_id=t2.table2_id SET t1.overview=t2.val WHERE t1.table1_id IN ( SELECT xxx FROM table2 WHERE table2_id=1);

顺便说一句，如果您只是从内部查询返回 table2_id ，则可以完全跳过内部查询。

Answer 3

显然，table2中有超过1条记录具有相同的ID。
但是，如果确定，请将=运营商更改为in运营商。
所以这将是你的代码：

UPDATE table1 AS t1 INNER JOIN table2 AS t2 ON t1.table1_id=t2.table2_id SET t1.overview=t2.val where t1.table1_id in ( SELECT table2_id
    FROM table2 WHERE table2_id=1);

修改不需要子查询，这是多余的。看看这个：

UPDATE table1 AS t1 INNER JOIN table2 AS t2 ON t1.table1_id=t2.table2_id SET t1.overview=t2.val where table2_id=1;

SQL数据库：＃1242 - 子查询返回超过1行

3 个答案: