MySQL查詢 - 子查詢返回多個1行錯誤

Question

我有一個表resources (title, resourceid)和另一個表classifications (title, resourceid, classificationid)

我想從資源增加瓷磚的分類表中，有與classifications同一resourceid多行。

當我寫此查詢

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

我得到這個錯誤：

Error - subquery returns more than 1 row.

Answer 1

嘗試通過標題分組的子查詢，即：

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