zoukankan      html  css  js  c++  java
  • SQL行列转换

    列转化成行
    --> --> (Roy)生成測試數據

    if not object_id('Class') is null
       
    drop table Class
    Go
    Create table Class([Student] nvarchar(2),[Course] nvarchar(2),[Score] int)
    Insert Class
    select N'张三',N'语文',78 union all
    select N'张三',N'数学',87 union all
    select N'张三',N'英语',82 union all
    select N'张三',N'物理',90 union all
    select N'李四',N'语文',65 union all
    select N'李四',N'数学',77 union all
    select N'李四',N'英语',65 union all
    select N'李四',N'物理',85
    Go

    动态:

    declare @s nvarchar(4000)
    set @s=''
    Select     @s=@s+','+quotename([Course])+'=max(case when [Course]='+quotename([Course],'''')+' then [Score] else 0 end)'
    from Class group by[Course]
    exec('select [Student]'+@s+' from Class group by [Student]')


    生成静态:

    select
       
    [Student],
       
    [数学]=max(case when [Course]='数学' then [Score] else 0 end),
       
    [物理]=max(case when [Course]='物理' then [Score] else 0 end),
       
    [英语]=max(case when [Course]='英语' then [Score] else 0 end),
       
    [语文]=max(case when [Course]='语文' then [Score] else 0 end)
    from
        Class
    group by [Student]

    GO

    /*
    Student 数学          物理          英语          语文
    ------- ----------- ----------- ----------- -----------
    李四      77          85          65          65
    张三      87          90          82          78

    (2 行受影响)
    */



    行转化成列
    if not object_id('Class') is null
       
    drop table Class
    Go
    Create table Class([Student] nvarchar(2),[数学] int,[物理] int,[英语] int,[语文] int)
    Insert Class
    select N'李四',77,85,65,65 union all
    select N'张三',87,90,82,78
    Go



    动态:

    declare @s nvarchar(4000)
    select @s=isnull(@s+' union all ','')+'select [Student],[Course]='+quotename(Name,'''')--isnull(@s+' union all ','') 去掉字符串@s中第一个union all
    +',[Score]='+quotename(Name)+' from Class'
    from syscolumns where ID=object_id('Class') and Name not in('Student')--排除不转换的列
    order by Colid
    exec('select * from ('+@s+')t order by [Student],[Course]')--增加一个排序

    生成静态:
    select *
    from (select [Student],[Course]='数学',[Score]=[数学] from Class union all
    select [Student],[Course]='物理',[Score]=[物理] from Class union all
    select [Student],[Course]='英语',[Score]=[英语] from Class union all
    select [Student],[Course]='语文',[Score]=[语文] from Class)t
    order by [Student],[Course]

    go

    /*
    Student Course Score
    ------- ------- -----------
    李四      数学      77
    李四      物理      85
    李四      英语      65
    李四      语文      65
    张三      数学      87
    张三      物理      90
    张三      英语      82
    张三      语文      78

    (8 行受影响)
    */
  • 相关阅读:
    eclipse安装WTP部署WEB项目
    BZOJ3302: [Shoi2005]树的双中心
    BZOJ2059: [Usaco2010 Nov]Buying Feed 购买饲料
    BZOJ1986: [USACO2004 Dec] Dividing the Path 划区灌溉
    BZOJ3126: [Usaco2013 Open]Photo
    51nod1486 大大走格子
    BZOJ1698: [Usaco2007 Feb]Lilypad Pond 荷叶池塘
    BZOJ2590: [Usaco2012 Feb]Cow Coupons
    BZOJ1739: [Usaco2005 mar]Space Elevator 太空电梯
    BZOJ2501: [usaco2010 Oct]Soda Machine
  • 原文地址:https://www.cnblogs.com/bobofsj11/p/1732715.html
Copyright © 2011-2022 走看看