title: mysql, make a group by for this case
body: <p>I have this data:</p>
  
  <pre><code>column1  |  column2  
  ____________________
  15           2013
  16           2012
  15           2012 //repeated
  15           2012 //repeated
  ...
  ...
  </code></pre>
  
  <p>I want to get this result</p>
  
  <pre><code>15     2013
  16     2013
  15     2012  //not repeated
  </code></pre>