SQL查询从一个表中选择不在另一表中的行

Question

Registraion and group_members

Registration Table
id  name  
-------                
1   A    
2   B    
3   C
4   D

group_members Table
name  Gid 
-------                
A   01    
B   01    
C   02

I need to get the names from registration table which are not a member in group_members table with Gid is 02 . The output must be obviously A,B and D . But I dont know how to achieve this.Please help.Thanks

Answer 1

Try this:

SELECT t1.*
FROM Registration AS t1
LEFT JOIN Group_members AS t2 ON t1.name = t2.name AND t2.Gid = '02'
WHERE t2.name IS NULL 

This will filter out any matching records in group_members table with Gid = '02' .

Answer 2

this should work

select name from
Registration reg where 
not exists 
(select null 
from group_members gm
where gm.name = reg.name
and gm.gid = '02')