题解 | #返回每个顾客不同订单的总金额#

select o.cust_id, oi.total_ordered
from Orders o join (select os.order_num,  sum(item_price * quantity) as total_ordered
                      from OrderItems os
                      group by order_num) oi
                 on o.order_num = oi.order_num
                 order by oi.total_ordered desc