题解 | #计算总和#
计算总和
http://www.nowcoder.com/practice/d8a624021183454586da94d280cc8046
select order_num,sum(item_price * quantity) total_price from OrderItems group by order_num having total_price>=1000 order by order_num
having 的使用是对于分组后的数据进行过滤，先有group by 然后再用having进行过滤，再对过滤后的数据进行排序，group by -having -order by
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