2_01_MSSQL课程_查询01

时间:2022-06-01 19:45:56

查询

  1.查询结果的别名

      列 as 别名 (建议用这种)

      列 别名

      别名=列

  Select sum(score1) as 成绩1,sum(score2)as  成绩2 from talScore

  2.聚合函数

    Avg()    Count()    Sum()  Min()/Max()

  Select max(score1),min(score1)from talScroe 

    “架构”信息,后面详细了解

  3.Top截取 和 Order排序

  Select * from talScore order by scoreId asc/desc,score2 asc/desc  (升序和降序)

  Select

  top 3 *,

    StuId as Demo,

  from

     talScore

   order by

    score1 desc

  4.去除重复:Distinct 

    select * from tabScroe

    select  distinct  score1 from talScroe order by score1  

    select distinct title,MiddleName from [SalesLT].[Customer] order by Title,MiddleName     ——title,MiddleName联合起来去重

  distinct 只能紧跟这select 后面,而且是对后面的所有的列都进行去重复操作