如何将这两行连接到SQL中的一列中

Question

在表中有两行，一个公共ID和不同的值。

例：

ID Response 
============= 
1 one 
1 two 
2 three 
3 four 

我怎样才能这两行Concat的成一列。

select 
    case 
     when multiple then row1 + ',' + row2 
     else Response 
    end as response 
from testtable 

预期输出：

response 
========== 
one,two  
three 
four 

SQL专家：我怎么能代替row1 + ',' + row2使此查询工作？

Answer 1

Select Id, Stuff((Select ','+Response from TableName B where B.Id=A.Id for Xml Path('')),1,1,'') as Response from TableName A 
group By Id; 

Sql Fiddle Demo

Answer 2

Declare @t table(id int,col1 varchar(20)) 
insert into @t values(1,'one'),(1, 'two'),(2, 'three'),(3, 'four') 
select distinct a.id, 
stuff((select ','+col1 from @t b where b.id=a.id for xml path('')),1,1,'')col1 
from @t a