Question

我正在尝试执行下面的mysql查询，我无法看到我做错了什么，我期望从查询的WHEN部分得到结果，而我从ELSE PART得到结果。

SELECT 
   CASE 
   WHEN `club_name` = '7' THEN (
      SELECT group_concat(DISTINCT mobile) from member WHERE `club_name` = '7'
   ) 
   ELSE (SELECT group_concat(mobile) from member) 
   END AS mobile 
FROM member

提前致谢。

Answer 1

我认为这是mysqls extensions to the group by statement烧伤的案例：

select list可以引用GROUP BY子句中未命名的非聚合列

...服务器可以自由选择每个组中的任何值，因此除非它们相同，否则所选的值是不确定的。 ......

SELECT 
   CASE 
   WHEN `club_name` = '7' THEN (
      SELECT group_concat(DISTINCT mobile) from member WHERE `club_name` = '7'
   ) 
   ELSE (SELECT group_concat(mobile) from member) 
   END AS mobile 
FROM member
GROUP BY mobile

SQL Fiddle

WITH GROUP BY返回（我相信你的追随者）

MOBILE
abc,def,def,xyz,xyz,xyz,lmn
abc,def,def,xyz,xyz,xyz,lmn
xyz,lmn
abc,def,def,xyz,xyz,xyz,lmn

没有分组：

MOBILE
abc,def,def,xyz,xyz,xyz,lmn
abc,def,def,xyz,xyz,xyz,lmn
abc,def,def,xyz,xyz,xyz,lmn
abc,def,def,xyz,xyz,xyz,lmn
xyz,lmn
xyz,lmn
xyz,lmn

只返回1行...

SELECT 
   CASE 
   WHEN `club_name` = '7' THEN (
      SELECT group_concat(DISTINCT mobile) from member WHERE `club_name` = '7'
   ) 
   ELSE (SELECT group_concat(mobile) from member) 
   END AS mobile 
FROM member
WHERE `club_name` = '7'
GROUP BY mobile

查询时MYSQL Select Case

1 个答案: