/*Write a SQL statement that produces all orders with the order number, customer name, commission rate and 
earned commission amount for those customers who carry their grade more than 200 and served by an existing salesman.*/
SELECT ord_no, cust_name, commission AS "Commission%",  
purch_amt*commission AS "Commission"  
FROM salesman,orders,customer  
WHERE orders.customer_id = customer.customer_id  
AND orders.salesman_id = salesman.salesman_id  
AND customer.grade>=200;