title: Finding salary same as roomate's
body: <p>There are three tables.
  Student, roommate, salary.  The colummns are as follows</p>
  
  <pre><code>student
  student_id (Primary Key) | smallint
  student_name             | varchar(30)
  
  roommate
  student_id (Primary Key) | smallint
  roommate_id              | smallint
  
  salary
  student_id (Primary Key) | smallint
  salary                   | float(10,2)
  </code></pre>
  
  <p>Now  I need to print the name of the students same as their roommates. 
  Well, I was able to find the people who have the same salary. But I am not able to find whether they are roommates or not. How to do this?</p>