title: SQL distinct field combination disregard the position
body: <p>Hi I have a SQL question:</p>
  
  <p>Table: Flight</p>
  
  <pre><code>Origin  Destination
  --------------------
  Boston    LA
  LA        Bostion
  Newyork   LA
  DC        Newyork
  </code></pre>
  
  <p>How could I select the distinct combination of the fight path if I do not care origin or destination: (Boston to LA) = (LA to Boston)</p>