MySQL：对列上的元素进行分组和展平

如果我有一个观点：

Movie             Genre    Actor
-------------------------------------------
Ocean's Twelve    Crime    George Clooney
Ocean's Twelve    Crime    Julia Roberts
Ocean's Twelve    Crime    Brad Pitt
Forrest Gump      Drama    Tom Hanks

我将如何按照电影标题进行分组,但是如此平整其他列：

Movie             Genre    Actor
-------------------------------------------
Ocean's Twelve    Crime    George Clooney, Julia Roberts, Brad Pitt
Forrest Gump      Drama    Tom Hanks

请注意,如果元素是等效的,则不会重复(例如Crime)

解决方法:

MySQL的

使用GROUP_CONCAT()函数：

SELECT movie, Genre, GROUP_CONCAT(Actor) AS Actor
FROM tableA
GROUP BY movie, Genre

SQL SERVER

SELECT A.movie, A.Genre, MAX(STUFF(B.ActorNames, 1, 1, '')) AS Actor
FROM tableA A 
CROSS APPLY(SELECT ' ' + Actor + ',' FROM tableA B 
            WHERE A.movie = B.movie AND A.Genre = B.Genre 
            FOR XML PATH('')
          ) AS B (ActorNames)
GROUP BY A.movie, A.Genre

标签：sql,mysql,group-by,select,group-concat
来源： https://codeday.me/bug/20190825/1717188.html