题解 | #返回每个顾客不同订单的总金额#

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

先连接表，再筛选