title: How do I group by for every rolling 3 rows in google cloud sql or python dataframe?
body: <p>Let's say I have a dataset.</p>
  
  <pre><code>Year | Month | Count
  2017 | 1     | 3
  2017 | 2     | 4
  2017 | 3     | 2
  2017 | 4     | 1
  2017 | 5     | 5
  2017 | 6     | 6
  </code></pre>
  
  <p>I want the group by result to be </p>
  
  <pre><code>group 1    | total count
  month1,2,3 |    9
  month2,3,4 |    7
  month3,4,5 |    8
  ...
  </code></pre>
  
  <p>I wonder is there a way to do this in google cloud SQL? if not, can I do this in python dataframe?</p>