题解 | #返回每个顾客不同订单的总金额#

#第一步对表OrderItems聚合
        # SELECT
        #     order_num,
        #     SUM(item_price * quantity) total_ordered
        # FROM
        #     OrderItems
        # GROUP BY
        #     order_num
#第二步表连接
select
cust_id
,tb.total_ordered
from(        SELECT
            order_num,
            SUM(item_price * quantity) total_ordered
        FROM
            OrderItems
        GROUP BY
            order_num) tb 
            inner join Orders o on tb.order_num=o.order_num
order by tb.total_ordered desc