title: select row that column2 not equal to column1
body: <p>I need help with a SQL Query</p>
  
  <p>I have this table</p>
  
  <pre><code>likes
   friend    friend2
        1          2
        2          1
        3          1
        4          5
  </code></pre>
  
  <p>I need to select only one pair of the friends that like each other.</p>
  
  <p>With my current select I'm obtaining this</p>
  
  <pre><code> id     name         id     name
  1709    Cassandra    1689   Gabriel 
  1689    Gabriel      1709   Cassandra
  1501    Jessica      1934   Kyle    
  1934    Kyle         1501   Jessica 
  </code></pre>
  
  <p>but the expected query result is:</p>
  
  <pre><code> id     name        id     name
  1709    Cassandra   1689    Gabriel 
  1501    Jessica     1934    Kyle    
  </code></pre>