mysql - SQL数据库: #1242 - Subquery returns more than 1 row

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

#1242 - Subquery returns more than 1 row

Answer 1

您需要一个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是固定的，为什么不直接使用1，比如:

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;