/*使用连接+分组查询*/
select cust_name, sum(item_price*quantity) total_price
from OrderItems oi
join Orders o
on oi.order_num=o.order_num
join Customers c
on c.cust_id=o.cust_id
group by cust_name
having sum(item_price*quantity)>1000   # 注意一般来说，不建议在having后面使用别名（从执行顺序上说）
order by total_price;   # order by 后面可以使用别名