if not object_id('tb') is null
    drop table tb
Go
Create table tb([id] int,[count] int,[name] nvarchar(1))
Insert tb
select 11,22,N'a' union all
select 11,22,N'b' union all
select 12,33,N'c' union all
select 12,33,N'd'
Go
select [id],
       [count],
       [name]=stuff((select ','+[name] 
                     from tb 
                     where [id]=t.[id] and [count]=t.[count]for xml path('')),1,1,'')
from tb t 
group by [ID],[count]

------解决方案--------------------
SQL code
if object_id('[tb]') is not null drop table [tb]
go
create table [tb]([id] int,[count] int,[name] varchar(1))
insert [tb]
select 11,22,'a' union all
select 11,22,'b' union all
select 12,33,'c' union all
select 12,33,'d'
 
---查询
select id,[count],
name=stuff((select ','+name from tb where id=t.id and [count]=t.[count] for xml path('')),1,1,'')
from tb t
group by id,[count]

/**
id          count       name
----------- ----------- ----------------
11          22          a,b
12          33          c,d

(2 行受影响)
**/

------解决方案--------------------

SQL code

/*------------------------------
--  Author : htl258(Tony)
--  Date   : 2010-04-16 11:06:38
--  Version: Microsoft SQL Server 2008 (RTM) - 10.0.1600.22 (Intel X86) 
    Jul  9 2008 14:43:34 
    Copyright (c) 1988-2008 Microsoft Corporation
    Developer Edition on Windows NT 5.1 <X86> (Build 2600: Service Pack 3)

------------------------------*/
--> 生成测试数据表:tb

IF OBJECT_ID('[tb]') IS NOT NULL
    DROP TABLE [tb]
GO
CREATE TABLE [tb]([id] INT,[count] INT,[name] NVARCHAR(10))
INSERT [tb]
SELECT 11,22,'a' UNION ALL
SELECT 11,22,'b' UNION ALL
SELECT 12,33,'c' UNION ALL
SELECT 12,33,'d'
GO
--SELECT * FROM [tb]

-->SQL查询如下:
create function fn_getstr(@id int,@count int)
returns varchar(20)
as
begin
  declare @s varchar(20)
  select @s=isnull(@s+',','')+name from tb where id=@id and @count=[count]
  return @s
end
go

select distinct id,[count],name=dbo.fn_getstr(id,[count]) from tb
/*
id          count       name
----------- ----------- --------------------
11          22          a,b
12          33          c,d

(2 行受影响)
*/