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返回每个顾客不同订单的总金额_牛客题霸_牛客网

思路：本题要求每个客户的下单总额，下单总额只需OrderItems一张表即可求出，而且Orders表中一个客户对应一个order_num，相对比较简单。

对OrderItems根据order_num进行分组，求出每个order_num对应的总金额即(sum(item_price*quantity)) total_ordered。查询 order_num,total_ordered两个字段作为mytable。

上述Orders表中一个客户对应一个order_num。所以用Orders表与mytable通过order_num进行左连接，去掉mytable中多余的数据。连接后查询cust_id和total_ordered即可。

sql：

select o.cust_id,mytable.total_ordered 
from Orders o left join 
(select order_num,(sum(item_price*quantity)) total_ordered from OrderItems group by order_num) mytable
on o.order_num=mytable.order_num 
order by total_ordered desc

思路或sql有误可在评论区指正哦~~~