title: How do I get the average of each similar column value?
body: <p>Say I have this:</p>
  
  <pre><code>     tag     value
  
  1    apple    3
  
  2    banana   5
  
  3    apple    4
  
  4    banana   2
  </code></pre>
  
  <p>How can I have a query get the average of each value with respect to the tags?</p>
  
  <p>So like:</p>
  
  <pre><code>    tag      value
  
  1   apple    3.5
  
  2   banana   3.5
  </code></pre>
  
  <p>I can get the average of the whole column easily with an inner select, but have no idea how to do so with respect to the tag.</p>