declare @t table 
(id int , chr char(1))

insert into @t
select 1, 'a' union 
select 1, 'h' union 
select 1, 'y' union 
select 4, 'k' union 
select 4, 'f' 


select * from @t

select distinct  id, STUFF((select  ''  +  cast(chr  as nvarchar(20)) from @t where id= t.id FOR XML PATH('')),1,0,'') 
from @t t