title: selecting distinct data with similar data in two columns
body: <p>I have a table <code>XXXTEST</code> </p>
  
  <pre><code>table XXXTEST (C1 varchar2(50),C2 varchar2(50), dist NUMBER )
  </code></pre>
  
  <p>with this sample data:</p>
  
  <pre><code>('Pune','Mumbai',128);
  ('Mumbai','Pune',128);
  ('Pune','Nashik',200);
  ('Nashik','Pune',200);
  ('Nashik','Mumbai',250);
  ('Nashik','Mumbai',250);
  </code></pre>
  
  <p>I want to select the city combination only once i.e from "pune-mumbai" and "mumbai-pune" only one row must be selected.</p>
  
  <p>I tried using self join but that didn't help. So please if you can provide with a query.</p>
  
  <p>Thanks in advance.</p>