IN子查询中的GROUP_CONCAT

Question

SELECT  A.id, A.title, 
FROM (`table`) as A
WHERE A.active = '1'
AND A.id IN (SELECT GROUP_CONCAT(B.id) from B where user = 3)

如果我仅启动子查询SELECT GROUP_CONCAT(B.id) from B where user = 3，我将获得1,2,3,4。但是，如果我启动整个查询，我只获得一行。

但是，如果我尝试用其值（1,2,3,4）替换子查询

SELECT  A.id, A.title, 
FROM (`table`) as A
WHERE A.active = '1'
AND A.id IN (1,2,3,4)

我获得了4行......正如我所需要的那样。

我的错误在哪里？

Answer 1

MySQL看到子查询只返回一个字段/行，因此将其视为：

... and A.id IN ('1,2,3,4')

归结为A.id = '1,2,3,4'。

对于'in'查询，不需要group_concat，只需执行：

... and A.id IN (select B.id FROM b where user = 3)

Answer 2

SELECT name
FROM test
WHERE salry
IN (

SELECT GROUP_CONCAT( CONCAT('''', salry,'''' ) ) 
FROM test group by salry
)

这个concat将使用单引号追加结果集，但仍然不能像salry一样工作在结果集'1000','2000','3000','40000' ...

Answer 3

使用FIND_IN_SET()

SELECT  A.id, A.title, 
FROM (`table`) as A
WHERE A.active = '1'
AND FIND_IN_SET(A.id,(SELECT GROUP_CONCAT(B.id) from B where user = 3))