MySQL查询 - 子查询返回多个1行错误

Question

我有一个表resources (title, resourceid)和另一个表classifications (title, resourceid, classificationid)

我想从资源增加瓷砖的分类表中，有与classifications同一resourceid多行。

当我写此查询

update `classification` 
set `title`= (select title 
       from Resources 
       where Resources.`resourceid` = classification.`resourceid`) 

我得到这个错误：

Error - subquery returns more than 1 row.

Answer 1

尝试通过标题分组的子查询，即：

UPDATE classification SET title=(SELECT title FROM Resources 
    WHERE Resources.resourceid=classification.resourceid GROUP BY title);