题解 | 返回每个顾客不同订单的总金额

select
    cust_id,
    sum(total_ordered) total_ordered
from
    (
        select
            cust_id,
            item_price * quantity total_ordered
        from
            OrderItems ori
            join Orders ord on ori.order_num = ord.order_num
    ) a
group by
    cust_id
order by
    total_ordered desc