题解 | #计算总和#

select order_num, total_price from 
(
select order_num, sum(item_price*quantity) as total_price 
from OrderItems 
group by order_num 
order by order_num
) t 
where total_price >= 1000;

先从表中将数据筛选出来，然后再对这个表进行条件查询。