title: Group by Time Interval
body: <p>I need to Group my Table into 15 minutes Intervals. I can do that with:</p>
  
  <pre><code>select dateadd(minute, datediff(minute, 0, ts) / 15 * 15, 0), sum (goodpieces) 
  from StationCount 
  Group by dateadd(minute, datediff(minute, 0, ts) / 15 * 15, 0)
  </code></pre>
  
  <p>But to display the returned data in a chart i need to insert also the intervals which don't have any data and aren't currently appearing in my select statement. How do i insert these?</p>