Write a SQL statement to make a list in ascending order for the salesmen who works either for one or more customer or not yet join under any of the customers.

Sample table: orders (Add this table as well in your database) ord_no purch_amt ord_date customer_id salesman_id 70001 150.5 2012-10-05 3005 70009 270.65 2012-09-10 3001 70002 65.26 2012-10-05 3002 70004 110.5 2012-08-17 3009 70007 948.5 2012-09-10 3005 70005 2400.6 2012-07-27 3007 70008 5760 2012-09-10 3002 70010 1983.43 2012-10-10 3004 70003 2480.4 2012-10-10 3009 70012 250.45 2012-06-27 3008 70011 75.29 2012-08-17 3003 70013 3045.6 2012-04-25 3002 5002 5005 5001 5003 5002 5001 5001 5006 5003 5002 5007 5001