题解 | #返回每个顾客不同订单的总金额#

select
  t1.cust_id,
  sum(t2.quantity * t2.item_price) as total_ordered
from
   Orders t1
  left join  OrderItems t2 on t2.order_num = t1.order_num
group by
  t1.cust_id
order by
  total_ordered desc

注意要Orders表左连接OrderItems