题解 | #返回每个顾客不同订单的总金额#

select
    cust_id,
    (
        select
            sum(quantity * item_price)
        from
            OrderItems
        where
            OrderItems.order_num = Orders.order_num
        group by
            order_num
    ) as total_ordered

from

    Orders
order by
    total_ordered desc;

把字段当作查询结果的子查询 不需要使用where in 了， 直接将查询结果作为一个字段返回