음 조건으로 검색한다면 이방법이 될듯한데염

declare @str varchar(8000)
set @str = ''

select @str =  @str + rtrim(product)+ ',' from product  where sale_seq=1
select @str

select T1.*, @str  as product, sum(price) as price from sale T1
join product T2 on T1.seq=T2.sale_seq
where sale_seq=1
group  by seq,customer,saler

create function get_string(@F1 char(1))
returns varchar(8000)
as
  begin
   declare @str varchar(8000)
   select @str = coalesce(rtrim(@str) + ', ' + convert(varchar,product) ,convert(varchar,product))
      from product
   where sale_seq = @F1
   return @str  
end

select distinct seq, customer,saler , dbo.get_string(seq) product , sum(price) as price
 from product T1 join sale T2 on T2.seq=T1.sale_seq
group  by seq,customer,saler 

핫..감사.. 감사합니다...