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  • 按某字段合并字符串

    描述:将如下形式的数据按id字段合并value字段。
    id    value
    ----- ------
    1     aa
    1     bb
    2     aaa
    2     bbb
    2     ccc
    需要得到结果:
    id     value
    ------ -----------
    1      aa,bb
    2      aaa,bbb,ccc
    即:group by id, 求 value 的和(字符串相加)
    */

    --1、sql2000中只能用自定义的函数解决
    create table tb(id int, value varchar(10))
    insert into tb values(1, 'aa')
    insert into tb values(1, 'bb')
    insert into tb values(2, 'aaa')
    insert into tb values(2, 'bbb')
    insert into tb values(2, 'ccc')
    go

    create function dbo.f_str(@id int) returns varchar(100)
    as
    begin
       
    declare @str varchar(1000)
       
    set @str = ''
       
    select @str = @str + ',' + cast(value as varchar) from tb where id = @id
       
    set @str = right(@str , len(@str) - 1)
       
    return @str
    end
    go

    --调用函数
    select id , value = dbo.f_str(id) from tb group by id

    drop function dbo.f_str
    drop table tb


    --2、sql2005中的方法
    create table tb(id int, value varchar(10))
    insert into tb values(1, 'aa')
    insert into tb values(1, 'bb')
    insert into tb values(2, 'aaa')
    insert into tb values(2, 'bbb')
    insert into tb values(2, 'ccc')
    go

    select id, [value] = stuff((select ',' + [value] from tb t where id = tb.id for xml path('')) , 1 , 1 , '')
    from tb
    group by id

    drop table tb


    --3、使用游标合并数据
    create table tb(id int, value varchar(10))
    insert into tb values(1, 'aa')
    insert into tb values(1, 'bb')
    insert into tb values(2, 'aaa')
    insert into tb values(2, 'bbb')
    insert into tb values(2, 'ccc')
    go
    declare @t table(id int,value varchar(100))--定义结果集表变量
    --
    定义游标并进行合并处理
    declare my_cursor cursor local for
    select id , value from tb
    declare @id_old int , @id int , @value varchar(10) , @s varchar(100)
    open my_cursor
    fetch my_cursor into @id , @value
    select @id_old = @id , @s=''
    while @@FETCH_STATUS = 0
    begin
       
    if @id = @id_old
          
    select @s = @s + ',' + cast(@value as varchar)
       
    else
         
    begin
           
    insert @t values(@id_old , stuff(@s,1,1,''))
           
    select @s = ',' + cast(@value as varchar) , @id_old = @id
         
    end
       
    fetch my_cursor into @id , @value
    END
    insert @t values(@id_old , stuff(@s,1,1,''))
    close my_cursor
    deallocate my_cursor

    select * from @t
    drop table tb

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  • 原文地址:https://www.cnblogs.com/zhanghaichang/p/1967277.html
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