mysql - #1054 - 'where 子句'中的未知列'a.group_id'

Question

为什么查询给我这个错误：#1054 - Unknown column 'a.group_id' in 'where clause'？

SELECT a.group_id
FROM message_private a
INNER JOIN (SELECT group_id,profile_id
     FROM message_group b
     WHERE a.group_id = b.group_id AND b.profile_id = 's'
) as b ON b.group_id = a.group_id 

Answer 1

您正在尝试在a导致错误的子查询中使用表别名。您应该能够通过以下方式编写查询：

SELECT a.group_id 
FROM message_private a 
INNER JOIN message_group b
  ON b.group_id = a.group_id 
WHERE b.profile_id = 's';

如果您需要子查询，则语法为：

SELECT a.group_id 
FROM message_private a 
INNER JOIN 
(
  SELECT group_id,profile_id 
  FROM message_group
  WHERE profile_id = 's'
) b 
  ON b.group_id = a.group_id