MySQL 子查询拉取多个结果

Question

我有不同 'manufacturer' 字段的重复记录。我正在尝试GROUP BY i.stocknumber，但这只会删除一条记录而不会收集其他制造商的结果。

有些记录有一个NULL 制造商字段，我尝试在子查询中使用GROUP_CONCAT 来省略“制造商”的不同结果。

这是我当前的查询：

SELECT i.id,i.stocknumber,m.manufacturer
FROM inventory i
INNER JOIN makes mk on i.make = mk.id 
INNER JOIN models md on i.model = md.id 
INNER JOIN classes cl on i.class = cl.id 
LEFT JOIN ( 
            SELECT idm.id, idm.inventory_id, dm.manufacturer AS 'manufacturer' 
            FROM display_manufacturers dm 
            INNER JOIN inventory_display_manufacturers idm ON dm.id = idm.display_manufacturer_id 
           ) m ON i.id = m.inventory_id 
-- GROUP BY i.stocknumber
ORDER BY i.stocknumber

我得到的结果是：

对通过连接manufacturer 字段对重复记录进行分组有什么想法吗？

（注意：我已经在子查询中尝试过GROUP_CONCAT）

预期结果：

id   | stocknumber | manufacturer
----------------------------------
946  | 011A        | NULL
907  | 1001        | Sports Coach, Coachmen
1032 | 1001x       | Sports Coach

等等……

Answer 1

你在找这个吗？

SELECT i.id, i.stocknumber, group_concat(distinct m.manufacturer) as manufacturers
. . .
GROUP BY i.stocknumber

编辑：

此版本明确将您的查询用作子查询。不应将所有制造商放在同一行：

select stocknumber, group_concat(distinct manufacturer) as manufacturers
from (SELECT i.id,i.stocknumber,m.manufacturer
      FROM inventory i
      INNER JOIN makes mk on i.make = mk.id 
      INNER JOIN models md on i.model = md.id 
      INNER JOIN classes cl on i.class = cl.id 
      LEFT JOIN ( 
            SELECT idm.id, idm.inventory_id, dm.manufacturer AS 'manufacturer' 
            FROM display_manufacturers dm 
            INNER JOIN inventory_display_manufacturers idm ON dm.id = idm.display_manufacturer_id 
           ) m ON i.id = m.inventory_id
     ) t
GROUP BY stocknumber ;

Answer 2

如果您要删除 NULL 字段，则只需添加一个 WHERE 条件，不包括 NULL 字段

SELECT i.id,i.stocknumber,m.manufacturer
FROM inventory i
INNER JOIN makes mk on i.make = mk.id 
INNER JOIN models md on i.model = md.id 
INNER JOIN classes cl on i.class = cl.id 
LEFT JOIN ( 
            SELECT idm.id, idm.inventory_id, dm.manufacturer AS 'manufacturer' 
            FROM display_manufacturers dm 
            INNER JOIN inventory_display_manufacturers idm ON dm.id = idm.display_manufacturer_id 
           ) m ON i.id = m.inventory_id 
WHERE m.manufacturer IS NOT NULL
-- GROUP BY i.stocknumber
ORDER BY i.stocknumber