select PaperID ,StudentID
from StudentsArrange
where PaperID in(select PaperID from……) //子查询
group by PaperID,StudentID
having count(PaperID)>1
from StudentsArrange
where PaperID in(select PaperID from……) //子查询
group by PaperID,StudentID
having count(PaperID)>1
select PaperID ,StudentID,count(PaperID)
from StudentsArrange
where PaperID in (select PaperID from……) //子查询
group by StudentID
having count(PaperID)>1
此语句必须要有sum或者count语句与之对应。
如果没有sum,则不能group by
道理是这样:聚组就是为了算和的。你将StudentID聚组了。PaperID 怎么显示啊!因为group by后一条StudentID只能显示一条,所以就是为了算和用的。
你在看看group by相关资料吧
我想你的意思是如果PaperID和StudentID都相同,只显示一次的PaperID和StudentID吧?
那么这么写:
select DISTINCT PaperID ,StudentID
from StudentsArrange