title: Get date diff then add 1 to each month in between
body: <p>What we're attempting to do is to get an accurate representation of the typical volume of orders in a month.
  Every following month (including the month the order was open) will have a count of 1 for that order until it was closed. 
  So for e.g. 2 orders were created in Feb 2017, thus February will have a count of 2. For order no. 4, every month following June will have a count of 1 for that particular order. </p>
  
  <pre><code>WAREHOUSENO ORDERNO ORDER DATE  CLOSED DATE
  1           ABC     2/22/17      3/10/17
  2           DEF     2/23/17      4/1/17
  1           GHI     3/1/17       3/28/17
  3           JKL     6/1/17  
  2           MNO     9/1/17       10/12/17
  3           PQR     10/22/17     2/23/18
  1           STU     12/5/17      12/28/17
  2           VWX     2/8/18  
  3           YZ      3/15/18
  </code></pre>
  
  <p>At the end we would like to sum all of the counts for each month, grouped by warehouse &amp; year.</p>
  
  <pre><code>     Month                                          
       WAREHOUSE    Jan   Feb   Mar  Apr  May Jun Jul Aug Sep Oct Nov Dec
           1          0    1     1     0   0    0  0   0   0   0   0   1
  2017     2          0    1     1     0   0    0  0   0   1   1   0   0
           3          0    0     0     0   0    1  1   1   1   2   2   2
  TOTAL OPEN               2     2              1  1   1   2   3   2   3
  
           1          0     0    0     0                          
  2018     2          1     1    1     1    
           3          1     1    2     2    
  TOTAL OPEN          2     1    3     3
  </code></pre>
  
  <p>Would really appreciate some direction with this! </p>