SQL 行列转换，sql2000和2005--多行转一行

SQL 行列转换，sql2000和2005--多行转一行

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http://jiang5311.blogbus.com/logs/53228755.html

以下主讲sql多行转为一列的合并问题，并在sql2000和2005得到验证，希望大家收藏！

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

--1. 创建表，添加测试数据

CREATE TABLE tb(id int, [value] varchar(10))

INSERT tb SELECT 1, 'aa'

UNION ALL SELECT 1, 'bb'

UNION ALL SELECT 2, 'aaa'

UNION ALL SELECT 2, 'bbb'

UNION ALL SELECT 2, 'ccc'

--SELECT * FROM tb

/**//*

id value

----------- ----------

1 aa

1 bb

2 aaa

2 bbb

2 ccc

(5 row(s) affected)

*/

--2 在SQL2000只能用自定义函数实现

----2.1 创建合并函数fn_strSum，根据id合并value值

GO

CREATE FUNCTION dbo.fn_strSum(@id int)

RETURNS varchar(8000)

AS

BEGIN

DECLARE @values varchar(8000)

SET @values = ''

SELECT @values = @values + ',' + value FROM tb WHERE

RETURN STUFF(@values, 1, 1, '')

END

GO

-- 调用函数

SELECT id, VALUE = dbo.fn_strSum(id) FROM tb GROUP BY id

DROP FUNCTION dbo.fn_strSum

----2.2 创建合并函数fn_strSum2，根据id合并value值

GO

CREATE FUNCTION dbo.fn_strSum2(@id int)

RETURNS varchar(8000)

AS

BEGIN

DECLARE @values varchar(8000)

SELECT @values = isnull(@values + ',', '') + value FROM tb WHERE

RETURN @values

END

GO

-- 调用函数

SELECT id, VALUE = dbo.fn_strSum2(id) FROM tb GROUP BY id

DROP FUNCTION dbo.fn_strSum2

--3 在SQL2005中的新解法

----3.1 使用OUTER APPLY

SELECT *

FROM (SELECT DISTINCT id FROM tb) A OUTER APPLY(

SELECT [values]= STUFF(REPLACE(REPLACE(

(

SELECT value FROM tb N

WHERE id = A.id

FOR XML AUTO

), '<N value="', ','), '"/>', ''), 1, 1, '')

)N

----3.2 使用XML

SELECT id, [values]=STUFF((SELECT ','+[value] FROM tb t WHERE id=tb.id FOR XML PATH('')), 1, 1, '')

FROM tb

GROUP BY id

--4 删除测试表tb

drop table tb

/**//*

id values

----------- --------------------

1 aa,bb

2 aaa,bbb,ccc

(2 row(s) affected)

*/