select cust_name,total_price
from Customers c
inner join(
select cust_id,sum(item_price*quantity) total_price
from OrderItems oi,Orders o
where oi.order_num = o.order_num
group by cust_id,oi.order_num
having total_price >= 1000) a
on c.cust_id = a.cust_id
order by total_price