题解 | #返回顾客名称和相关订单号以及每个订单的总价#

select
    T1.cust_name,
    T1.order_num,
    T2.OrderTotal
from
    (
        select
            Customers.cust_name,
            Orders.order_num
        from
            Customers
            left join Orders on Orders.cust_id = Customers.cust_id
    ) T1
    left join (
        select
            order_num,
            sum(quantity * item_price) as OrderTotal
        FROM
            OrderItems
        GROUP BY
            order_num
    ) T2 on T1.order_num = T2.order_num
order by
    T1.cust_name