with t1 as (select cust_name,c.cust_id as cust_id,order_num from Customers c
join
Orders
on c.cust_id = Orders.cust_id),

t2 as (select t1.order_num as order_num,quantity*item_price as OrderTotal,cust_name from OrderItems
join t1
on t1.order_num = OrderItems.order_num)

select cust_name,order_num,OrderTotal from t2
order by cust_name,order_num