title: Filter records by year and month where year and month are columns in the table
body: <p>So I have this specific table structure</p>
  
  <pre><code>State_Code | ColA | ColB | Year | Month
  ----------  ------  ----  ------  -----
  AK            5      3     2013   4
  AK            6      1     2014   8
  AK            3      4     2012   9
  .
  .
  .
  .
  .
  </code></pre>
  
  <p>I do not have access to change the table structure.
  The required query is described as follows</p>
  
  <p>Find total ColA, ColB for each state between the last 12 months and the last 24 months.</p>
  
  <p><strong>Questions</strong>
  Is it possible to get such a query done without using stored procedures.
  I can frame a query using add_months for getting the right year, but I can't get around the logical issue of selecting the month range.</p>