select ID,Name 
from Users as user
left join Admin as ad on user.Id=ad.Id

select ID,C_Name 
from Group as grou
left join Group as cg on grou.ID=cg.serial

select * from (
    select ID,Name 
    from Users as user
    left join Admin as ad on user.Id=ad.Id) a 
inner join (
    select ID,C_Name 
    from Group as grou
    left join Group as cg on grou.ID=cg.serial
) on a.ID = b.ID

------解决方案--------------------

SQL code


select * from (
    select ID,Name 
    from Users as users
    left join Admin as ad on users.Id=ad.Id) a 
inner join (
    select ID,C_Name 
    from [Group] as g
    left join [Group] as cg on g.ID=cg.serial
) b on a.ID = b.ID