如何使用选择查询的GROUP_CONCAT子查询在MySQL

Question

我有3个表：

tbl_user存储所有用户信息（USER_ID，姓名，地址）

user_id name  address 
1   a (shop)  home 
2   b (shop) bakerstreet 
3   c (staff) wallstreet 
4   d (staff) georgia 
5   e (staff) sydney 

tbl_user_group存储用户类型（USER_ID， USER_TYPE：1 = shop_owner，2 =人员）

user_id user_type 
1    1 
2    1 
3    2 
4    2 
5    2 

tbl_user_association保持shop_owner和工作人员的关系（shop_owner_id，staff_id）

shop_owner_id staff_id 
1    3 
1    4 
1    5 
2    3 
2    4 

期望结果

我想显示员工和它们与如下相关联的相应店铺的列表：

user_id staff_name shop_owner 
3   c    a,b 
4   d    a,b 
5   e    a 

我使用GROUP_CONCAT如上所述here试过。查询如下：

SELECT 
u.id       AS user_id, 
u.name      AS staff_name, 
(SELECT GROUP_CONCAT(u.name separator ',') FROM tbl_user u WHERE u.id = ua.shop_owner_id) AS 
shop_owner 
FROM tbl_user u 
JOIN tbl_user_group ug ON u.id = ug.user_id 
LEFT JOIN tbl_user_association ua ON u.id = ua.staff_id 
WHERE ug.user_type = 2 
GROUP BY u.id 

但它返回如下人员的单行。我哪里出错了？

user_id staff_name shop_owner 
3    c  a 
4    d  a 
5    e  a 

Answer 1

这是我会怎么做它：

SELECT 
    u.user_id, 
    u.name, 
    GROUP_CONCAT(so.name) 
FROM 
    tbl_user_group ug 
    INNER JOIN tbl_user u 
     ON (ug.user_id = u.user_id) 
    INNER JOIN tbl_user_association ua 
     ON (ua.staff_id = u.user_id) 
    INNER JOIN tbl_user so -- here join again the user table to get shop owners names 
     ON (ua.shop_owner_id = so.user_id) 
WHERE 
    ug.user_type = 2 
GROUP BY 
    u.user_id;