title: How do I remove a duplicate from a SELECT DISTINCT over multiple columns?
body: <p>I have the following select statement:</p>
  
  <pre><code>SELECT DISTINCT a.month, 
                  a.date 
             FROM a 
         ORDER BY a.bar DESC NULLS LAST; 
  </code></pre>
  
  <p>month is a char, date is a date. I need to use the date column because that's the thing i'm ordering the results by. I'm getting this result:</p>
  
  <pre><code>foo | bar
  
   x---|---20-nov-15 00:00:00  
   y---|---31-oct-15 00:00:00  
   y---|---30-oct-15 00:00:00  
   z---|---28-sept-15 00:00:00
  </code></pre>
  
  <p>I am in need of a <code>WHERE</code> statement that would eliminate that duplicate Y from the result, I've been looking everywhere and couldn't find a solution</p>