text: select
   100.00 * sum(case
   when p_type like 'PROMO%'
   then l_extendedprice * (1 - l_discount)
   else 0
   end) / sum(l_extendedprice * (1 - l_discount)) as promo_revenue
  from
   lineitem,
   part
  where
   l_partkey = p_partkey
   and l_shipdate >= date '1995-09-01'
   and l_shipdate < cast('1995-10-01' as date);
  