题解 | #返回每个顾客不同订单的总金额#

select
    b1.cust_id cust_id,
    total_ordered
from
    (
        select
            order_num,
            sum(item_price * quantity) total_ordered
        from
            OrderItems
        group by
            order_num
    ) a1
    join Orders b1 on a1.order_num = b1.order_num
order by
    total_ordered desc;

子查询返回total_ordered，通过分组聚合，等值连接