title: Count the number of occurences of a comma separated string
body: <p>I am needing a way to count comma separated values like this - any
  suggestions please?</p>
  
  <p>Table:</p>
  
  <pre><code>id (int) | site (varchar)
  1        | 1,2,3
  2        | 2,3
  3        | 1,3
  </code></pre>
  
  <p>Desired output:</p>
  
  <pre><code>site | # of occurrences
  1    | 2
  2    | 2
  3    | 3
  </code></pre>