title: difference between ON Clause and using clause in sql
body: <p>I am doing some assignment related to joins in oracle.
  In some point I stucked i.e. what is the difference between USING and ON clause.</p>
  
  <p>I know that using ON clause we are able to join unlimited tables. 
  Is it possible to join unlimited tables using USING clause?how?
  could you explain it by using example.</p>