--给列改名
方法1.
select sName as '姓名',sAge as '年龄' from student
方法2.
select sName '姓名',sAge '年龄' from student
方法3.
select '姓名'=sName,'年龄'=sAge from student
--Top Distinct
select top 2 sName,sAge,sSex from student
order by sAge
--百分之10个学生 如果有小数位数,直接进1
select top 10 percent sName,sAge,sSex
from student
select distinct * from student
select distinct sName from student
select distinct sName,sSex,sAge from student --distinct只有当所有的列都重复时,才会剔除