有表tb, 如下：
id    value
1     aa
1     bb
2     aaa
2     bbb
2     ccc
需要得到结果：
id     values
1      aa,bb
2      aaa,bbb,ccc
即，group by id, 求value 的和（字符串相加）
1. 旧的解决方法
-- 1. 创建处理函数
CREATE FUNCTION dbo.f_str(@id int)
RETURNS varchar(8000)
AS
BEGIN
    DECLARE @r varchar(8000)
    SET @r = ''
    SELECT @r = @r + ',' + value
    FROM tb
    WHERE id=@id
    RETURN STUFF(@r, 1, 1, '')
END
GO
-- 调用函数
SELECt id, values=dbo.f_str(id) 
FROM tb 
GROUP BY id
-- 2. 新的解决方法
-- 示例数据
DECLARE @t TABLE(id int, value varchar(10))
INSERT @t SELECT 1, 'aa'
UNION ALL SELECT 1, 'bb'
UNION ALL SELECT 2, 'aaa'
UNION ALL SELECT 2, 'bbb'
UNION ALL SELECT 2, 'ccc'
-- 查询处理
SELECT *FROM (SELECT DISTINCT Id FROM @t)A
OUTER APPLY(
    SELECT [values]= STUFF(REPLACE(REPLACE(
            (   SELECT value FROM @t N
                WHERE id = A.id
                FOR XML AUTO
             ), '<N value="', ','), '"/>', ''), 1, 1, '')
)N
/*--结果
id          values
----------- ----------------
1           aa,bb
2           aaa,bbb,ccc
(2 行受影响)
--*/

------解决方案--------------------
SQL code

--> 测试数据：[tbl]
if object_id('[tbl]') is not null drop table [tbl]
create table [tbl]([id] int,[value] varchar(5))
insert [tbl]
select 1,'alex' union all
select 1,'david' union all
select 2,'susan' union all
select 2,'linda'

-- 1. 创建处理函数
GO
CREATE FUNCTION dbo.f_str(@id int)
RETURNS varchar(8000)
AS
BEGIN
    DECLARE @r varchar(8000)
    SET @r = ''
    SELECT @r = @r + ',' + value
    FROM [tbl]
    WHERE id=@id
    RETURN STUFF(@r, 1, 1, '')
END
GO
-- 调用函数
SELECt id, [value]=dbo.f_str(id) 
FROM [tbl] 
GROUP BY id
/*
id    value
1    alex,david
2    susan,linda
*/

------解决方案--------------------
SQL code
/****************************************************************************************************************************************************** 
合并分拆表数据 

整理人：中国风(Roy) 

日期:2008.06.06 
******************************************************************************************************************************************************/ 

--> --> (Roy)生成測試數據 

if not object_id('Tab') is null 
    drop table Tab 
Go 
Create table Tab([Col1] int,[Col2] nvarchar(1)) 
Insert Tab 
select 1,N'a' union all 
select 1,N'b' union all 
select 1,N'c' union all 
select 2,N'd' union all 
select 2,N'e' union all 
select 3,N'f' 
Go 

合并表: 

SQL2000用函数: 

go 
if object_id('F_Str') is not null 
    drop function F_Str 
go 
create function F_Str(@Col1 int) 
returns nvarchar(100) 
as 
begin 
    declare @S nvarchar(100) 
    select @S=isnull(@S+',','')+Col2 from Tab where Col1=@Col1 
    return @S 
end 
go 
Select distinct Col1,Col2=dbo.F_Str(Col1) from Tab 

go 

SQL2005用XML: 

方法1: 

select 
    a.Col1,Col2=stuff(b.Col2.value('/R[1]','nvarchar(max)'),1,1,'') 
from 
    (select distinct COl1 from Tab) a 
Cross apply 
    (select COl2=(select N','+Col2 from Tab where Col1=a.COl1 For XML PATH(''), ROOT('R'), TYPE))b 

方法2: 

select 
    a.Col1,COl2=replace(b.Col2.value('/Tab[1]','nvarchar(max)'),char(44)+char(32),char(44)) 
from 
    (select distinct COl1 from Tab) a 
cross apply 
    (select Col2=(select COl2 from Tab  where COl1=a.COl1 FOR XML AUTO, TYPE) 
                .query(' <Tab> 
                {for $i in /Tab[position() <last()]/@COl2 return concat(string($i),",")} 
                {concat("",string(/Tab[last()]/@COl2))} 
                </Tab>') 
                )b 

SQL05用CTE: 

;with roy as(select Col1,Col