Use something like this:

with basedata as (

select distinct

FK_ID

from

dbo.MyTable

)

select

FK_ID,

NewVal = stuff((select ',' + Value

from dbo.MyTable mt

where mt.FK_ID = bd.FK_ID

order by mt.ID

for xml path(''),TYPE).value('.','varchar(max)'),1,1,'')

from

basedata bd;