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
, t1.order_num
, sum(quantity*item_price) OrderTotal
from Orders t1
left join Customers c on t1.cust_id = c.cust_id
left join OrderItems t2 on t1.order_num = t2.order_num
group by 1,2
order by 1,2