text: select
  	c_custkey,
  	c_name,
  	sum(l_extendedprice * (1 - l_discount)) as revenue,
  	c_acctbal,
  	n_name,
  	nation.population,
  	c_address,
  	c_phone,
  	c_comment
  from
  	customer,
  	orders,
  	lineitem,
  	nation
  where
  	c_custkey = o_custkey
  	and l_orderkey = o_orderkey
  	and o_orderdate >= date '1993-03-01'
  	and o_orderdate < date '1993-03-01' + interval '3 month'
  	and l_returnflag = 'R'
  	and c_nationkey = n_nationkey
  	and nation.population>1000000
  group by
  	c_custkey,
  	c_name,
  	c_acctbal,
  	c_phone,
  	n_name,
  	nation.population,
  	c_address,
  	c_comment
  order by
  	revenue desc
  limit 20;