题解 | #返回顾客名称和相关订单号以及每个订单的总价#

select cust_name, order_num, (sum(quantity * OI.item_price)) OrderTotal
from (Customers
    inner join Orders USING (cust_id) inner join OrderItems OI USING (order_num))
group by cust_name, order_num
order by cust_name, order_num;