题解 | #计算总和#
返回每个顾客不同订单的总金额
http://www.nowcoder.com/practice/ce313253a81c4947b20e801cd4da7894
因为表中没有total_ordered,我们先使用sum构造出来，然后两个表做内连接Join..on条件，连接条件是order_num.desc表示降序排列。 以下是代码：
select cust_id,total_ordered
from Orders o
join
(select
cust_num,sum(order_item *quantity) total_ordered
from OrderItms
group by order_num
)t
on o.order_num = t.order_num
order by total_ordered desc;
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