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