使用having条件语句，附加SQL执行的顺序：

From..... → where条件语句 → group by 分组 → sum、avg等聚合函数计算 → having条件语句 → order by 排序语句

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