题解 | #返回每个顾客不同订单的总金额#
返回每个顾客不同订单的总金额
https://www.nowcoder.com/practice/ce313253a81c4947b20e801cd4da7894
select t2.cust_id,sum(t1.item_price*t1.quantity) as total_ordered from OrderItems t1 left join Orders t2 on t1.order_num = t2.order_num group by t2.cust_id having t2.cust_id is not NULL order by total_ordered DESC
这里使用了Left join 的方式，来进行多表查询，选择OrderItems表作为驱动表，查询条件为 t1.order_num = t2.order_num
，找出符合条件的数据，但是还要保证右表的t2.cust_id不能为空。这是需要过滤的数据
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