题解 | 返回顾客名称和相关订单号以及每个订单的总价

select c.cust_name,o.order_num,sum(item_price*quantity) as OrderTotal from Customers c join Orders o on
c.cust_id=o.cust_id join OrderItems oi on
o.order_num=oi.order_num
group by c.cust_name,o.order_num
order by c.cust_name,o.order_num asc;