title: SQL determine if a number of consecutive months have passed
body: <p>I have 3 columns 1 indicating agent id, one indicating which level they are (Beginner, Intermediate, Advanced) and on indicate the month end date they reached that level.</p>
  
  <p>If the sample data looks like this</p>
  
  <pre><code>360123, Beginner, 1/22/2011
  360123, Null, 2/22/2011
  360123, Beginner, 3/22/2011
  360123, Intermediate, 4/22/2011
  360123, Beginner, 5/22/2011
  360123, Beginner, 6/22/2011
  </code></pre>
  
  <p>How do I design a query which will tell me which agents made all the beginner goals for 4 consecutive months from 3/22 to 6/22?</p>
  
  <p>Wow, thank you all for the help!</p>
  
  <p>How about for 4 months out of a 6 month period where the first month is any month you hit one of the goals?</p>