title: Calculating number of full months between two dates in SQL
body: <p>I need to calculate the number of <em>FULL</em> month in SQL, i.e.</p>
  
  <ul>
  <li>2009-04-16 to 2009-05-15 => 0 full month</li>
  <li>2009-04-16 to 2009-05-16 => 1 full month</li>
  <li>2009-04-16 to 2009-06-16 => 2 full months</li>
  </ul>
  
  <p>I tried to use DATEDIFF, i.e.</p>
  
  <pre><code>SELECT DATEDIFF(MONTH, '2009-04-16', '2009-05-15')
  </code></pre>
  
  <p>but instead of giving me full months between the two date, it gives me the difference of the month part, i.e.</p>
  
  <pre><code>1
  </code></pre>
  
  <p>anyone know how to calculate the number of full months in SQL Server?</p>