这个问题那么难吗？不好意思，第三次问 =.=

Question

delete
    news
from
    news a,
    user b
where
    b.userid = a.postuserid
    and
    datediff(hh,user.joindate,getdate()) < 24

Answer 1

delete t
FROM News t 
where exists(select * from [User] u where u.UserID = t.PostUserid
and (DATEDIFF(hh, u.JoinDate, GETDATE()) < 24) )

Answer 2

study 
you can try this : don't use biemingdelete
FROM News  
where exists(select * from User   where User.UserID = News.PostUserid
and (DATEDIFF(hh, User.JoinDate, GETDATE()) < 24) )
then
 use anthor bieming
try

Answer 3

delete
    news
from
    news a,
    [user] b
where
    b.userid = a.postuserid
    and
    datediff(hh,b.joindate,getdate()) < 24就可以了