承德市网站开发/网络营销概述ppt

–查询tsID降序排列的前五个学生
select top 5 * from TblStudent order by tsID desc
desc是降序排列，如果不写，则默认为升序，asc

–查询结果合并为一列
select top 5
tsAddress+’ ‘+tsName as studentName
from TblStudent order by tsID desc
–按百分比求，向上取整
select top 10 percent * from TblStudent order by tsID desc

–distinct去除重复，
select distinct
tsName,tsAddress,tsClassID
from TblStudent

如果查询结果的所有列都重复，则去除重复，只是显示的结果去除重复，不影响数据库的内容