title: How to get the unique set of count for rows with different values for a certain hour
body: <p>select id, hour, count from stats;</p>
  
  <pre><code>1, 0, 2
  2, 0, 20
  3, 1, 10
  4, 1, 20 
  5, 2, 10
  5, 2, 30
  </code></pre>
  
  <p>I would want the output (hour, count) to render as</p>
  
  <pre><code>0, 22
  1, 30
  2, 40
  </code></pre>
  
  <p>How do I perform a unique count for the hour interval?</p>