title: Mysql Fetching unique conversation users
body: <p>My current table structure</p>
  
  <p>Table private_messages</p>
  
  <pre><code>id     user_to     user_from      message      time_sent
   1           1             2         Test       ~DateTime
   2           2             1        Test2       ~DateTime
  </code></pre>
  
  <p>How can I filter out the unique conversations on basis of a user_to or user_from id? </p>
  
  <p>So thats a conversation between 2 ppl user_a and user_b 
  returns user_b in POV of user_a
  returns user_a in POV of user_b</p>
  
  <p>If I query from POV of user_to I would like to receive something like this</p>
  
  <pre><code>User_id      last_message_sent      time_sent
        2                  Test2          ~Last time sent
  </code></pre>