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 >= '1995-09-01'
    and l_shipdate < '1995-10-01';
  