title: Cumulative Sum of Count
body: <p>I would like to know whether a cumulative sum over a count is possible. An example I would like to work with is storms that affected the US this year. I would like a result-set that lists the months in 2014, along with the cumulative sum of storms that affected the US until that month. I am hoping to get something 3 columns - Month, NumberofStorms and CumulativeSum that look like this:</p>
  
  <pre><code>Month        NumberofStorms     CumulativeSum
  -----------------------------------------------
  Jan              2                   2
  Feb              1                   3
  Mar              1                   4
  Apr              0                   4
  May              0                   4
  Jun              0                   4
  Jul              0                   4
  Aug              0                   4    
  Sep              1                   5
  Oct              3                   8
  Nov              5                  13 
  Dec              8                  21
  </code></pre>
  
  <p>How can I achieve this? </p>