Sql--order by、desc降序、top
———通过order by 语句进行排序:
–1.降序order by 列名desc
–2.升序order by 列名 或order by 列名asc
–3.order by语句必须一定要放在整个sql语句的最后。
–4.根据多列进行排序
–5.可以按照表达式进行排序
–现根据英语成绩排序,再根据数学成绩排序(先按照英语成绩排序,当英语成绩相同的时候再按照数学成绩排序)
select * from TblScore order by tEnglish desc,tmath desc
select * from TblStudent order by tsage desc –降序排序
select * from TblStudent order by tsage asc –升序排序
select * from TblStudent order by tsage –默认就是升序排序
–top
–查询数学成绩最高的5名
select top 5 * from TblScore order by tMath desc
–获取数学成绩最低的5名
select top 5 * from TblScore order by tMath asc
–如果top后跟的不是数字,而是一个表达式一定要使用()把表达式括起来。
select top (2*2) * from TblScore order by tMath desc
–查询出前35%数据。
select top 35 percent * from TblScore order by tMath desc
select*,平均分=(tEnglish+tmath)*1.0/2 from TblScore order by 平均分 desc
select*from TblScore order by (tEnglish+tmath)*1.0/2 desc