用临时表代替游标实现多条数据的动态更新

 想根据一个结果集来更新表中的字段，也就是这个意思：

update a set a.s=b.ss,a.f=b.ff where id in (select id from b where xxx)

我的第一想法是使用游标。结果发现游标的效率太低了。经高人指点使用了临时表

代码：

 1 declare @t table(userid int,username nvarchar(50),commenttime datetime,questionid nvarchar(50))
 2 
 3 insert @t(userid,username,commenttime,questionid)
 4 select userid,username,commenttime,questionid from comment c
 5 where questionid in(
 6 select questionId from  question
 7 where CreateTime<DATEADD(minute,1440,getdate())
 8 and IsAutoAdd=100 and questionstatus<>1)
 9 and not   exists
10 (select 1 from comment where questionid=c.questionid and commenttime> c.commenttime);
11 
12 
13     update question set lastcommentuserID=t.userid,
14                         lastcommentuserName=t.username,
15                         LastCommentTime=t.commenttime
16                     from @t t
17                         where question.questionID=t.questionid

18 --set @error=@error+@@error;