php – MySQL列出用户及其组

在MySql数据库中我有表用户

user_id | user_name
--------+----------
1       | Joe
2       | Anna
3       | Max

表组

group_id | group_name
---------+----------
1        | Red
2        | Blue
3        | Green

表group_member

group_member_id | user_id | group_id
----------------+---------+---------
1               | 1       | 2
2               | 3       | 2
3               | 1       | 3 
3               | 2       | 1

所以… Red组的成员是Anna,Green gorup的成员是Joe,Blue组的成员是Joe和max.

如何获取用户及其组的列表

User  | Group
------+------------
Joe   | Green, Blue
Anna  | Red
Max   | Blue 

解决方法:

SELECT u.user_name, GROUP_CONCAT(g.group_name)
FROM `user` u
inner JOIN group_member gm on gm.user_id = u.user_id
inner JOIN `group` g on g.group_id = gm.group_id
group by u.user_id

标签：concat,php,mysql,group-concat
来源： https://codeday.me/bug/20190902/1789433.html