title: SQL Server - Cross join with where / on condition
body: <p>I have a table with monthly data for employees that I'd like to do cross joins but only after making sure they're in the same month.  Table looks like this:</p>
  
  <pre><code>  Month      Emp_id
  1/1/2017      123
  1/1/2017      234
  1/1/2017      345
  1/1/2017      456
  2/1/2017      123
  2/1/2017      234
  2/1/2017      345
    ...
  </code></pre>
  
  <p>I'd like to do something like this:</p>
  
  <pre><code>select *
  from t1
  cross join t1 as t2
     on t1.Month = t2.Month
  </code></pre>
  
  <p>Is there a way to do this?</p>
  
  <p>EDIT:</p>
  
  <p>To elaborate,  if I have 100 employees in each month and 12 months I'm looking to get an output table with 120,000 rows (100 * 100 Cartesian for each month, times 12 (1 for each month) instead of doing a full Cartesian which would be 1,440,000.</p>