title: Kusto query for time difference
body: <p>If have a question about the kusto query language. When I query for a certain custom event (messages), I get a list of these events. Each message belongs to a certain conversation. I would like see the duration of each conversation.</p>
  
  <p>To put it simple, if this is my sample data:</p>
  
  <pre><code>Timestamp          ConversationID
  8-5-2020 12:45:37  9mCksoeRrG1KbHoRIWWq-h    
  8-5-2020 12:45:39  9mCksoeRrG1KbHoRIWWq-h    
  8-5-2020 13:29:12  5noGScSZcJZqgzmVDMWZ-h   
  8-5-2020 13:29:14  5noGScSZcJZqgzmVDMWZ-h  
  8-5-2020 13:29:17  5noGScSZcJZqgzmVDMWZ-h    
  8-5-2020 13:29:23  5noGScSZcJZqgzmVDMWZ-h   
  </code></pre>
  
  <p>I would like to see this:  </p>
  
  <pre><code>ConversationID          Duration  
  9mCksoeRrG1KbHoRIWWq-h  2(seconds?)   
  5noGScSZcJZqgzmVDMWZ-h  11(seconds?)
  </code></pre>
  
  <p>How can I achieve this?</p>
  
  <p>Thank you!<br>
  Regards, 
  Tom</p>