DECLARE @group TABLE

(

  [values] varchar(8000),

  [group] int

)

if exists (select * from tempdb.sys.tables t where t.name like '#groups%')

 drop table dbo.#groups

;with a(value, [group])

as

(

select * from (values ('a', 1), ('b', 1), ('c', 1), ('d', '2'), ('e', 2)) a(value, [group])

)

select * into #groups from a

--select * from #groups

insert into @group select distinct null, [group] from #groups

declare @g int

declare cur cursor for select [group] from @group

open cur

fetch next from cur into @g

WHILE(@@FETCH_STATUS=0)

BEGIN

declare @str varchar(8000) = ''

select @str += ' ' + value from #groups where [group] = @g

--select @str a

update @group set [values] = @str where [group] = @g

fetch next from cur into @g

END

CLOSE CUR

DEALLOCATE CUR

select * from @group