如何检查表是否在另一个表中有匹配的记录？

Question

我有以下表：

表1：AccessMenu

userid item 

1  a 

2  b  

2  c 

和

表2：ActionRights

idAdmin itemCol 

2   v 

2   m 

2   d 

DESIRED RE SULT：

userid  yes/no 

    1   no 

    2   yes 

当我在ActionRight匹配userid到idadmin它应该返回Yes否则No。

我想下面的查询：

select AccessMenu.userid, 
case when ActionRights.IdAdmin=AccessMenu.userid then 'Yes' else 'No' end as 'GRP' 
from AccessMenu left join ActionRights 
on ActionRights.IdAdmin =AccessMenu.userid 

但通过这个查询我收到重复的结果为：

userid  yes/no 

    1   no 

    2   yes 

    2   yes 

    2   yes 

    2   yes 

    2   yes 

请帮助我。

Answer 1

SELECT userid, 
     CASE 
     WHEN idadmin IS NULL THEN 'No' 
     ELSE 'Yes' 
     END AS 'Grp' 
FROM (SELECT accessmenu.userid AS UserId, 
       actionrights.idadmin AS IdAdmin 
     FROM accessmenu 
       LEFT JOIN actionrights 
         ON actionrights.idadmin = accessmenu.userid)z 

Answer 2

请检查使用子查询：

select distinct 
    userid, 
    case when (SELECT COUNT(*) from ActionRights b where b.idAdmin=a.userid)>0 then 'Yes' else 'No' end [Yes/No] 
from AccessMenu a 

Answer 3

试试这个

SELECT distinct UserId, CASE WHEN IsAdmin IS NULL THEN 'No' ELSE 'Yes' END AS 'Grp' 
FROM ( 
     select AccessMenu.userid as UserId ,ActionRights.IsAdmin as IsAdmin 
     from AccessMenu left join ActionRights 
     on ActionRights.IsAdmin =AccessMenu.userid 
    )a 

看一看

http://www.sqlfiddle.com/#!2/07d52/10

Answer 4

它很简单。不需要内部查询或子查询。只取 鲜明

SELECT DISTINCT AM.USERID, 
CASE WHEN AR.USERID IS NULL THEN 'NO' ELSE 'YES' END AS [YES/NO] 
FROM #ACCESSMENU AM 
LEFT JOIN #ACCESSRIGHT AR ON AM.USERID=AR.USERID