String Concatenation

Concatenate multiple rows into a comma delimited string.

declare @table table (
id int
,val varchar(2)
)
insert @table
Values (1 ,'a'),
(1,'b'),
(1,'c'),
(1,'d'),
(2,'a'),
(2,'b'),
(2,'c'),
(3,'a'),
(3,'b')


select id, stuff((
select (','+val) from @table q1
where q1.id = q2.id
for xml path('')),1,1,'') val
from @table q2
group by q2.id