/*16. Write a query to find the salesmen who have multiple customers.*/
SELECT *   
FROM salesman   
WHERE salesman_id IN (  
   SELECT DISTINCT salesman_id   
   FROM customer a   
   WHERE EXISTS (  
      SELECT *   
      FROM customer b   
      WHERE b.salesman_id=a.salesman_id   
      AND b.cust_name<>a.cust_name));