title: Access SQL: Calculating Min date value and duration for each day
body: <p>I'm looking at GPS data for vehicles, composed of the following information:</p>
  
  <pre><code>vehicle        day              ignition   landmark
  ---------------------------------------------------
  Sample Guy 1   7/5/2013 14:32   on         
  Sample Guy 1   7/5/2013 15:10   off        Random Place B
  Sample Guy 1   7/5/2013 15:15   on         Random Place B
  Sample Guy 1   7/5/2013 15:20   off
  Sample Guy 1   7/20/2013 18:14  on
  Sample Guy 1   7/20/2013 18:20  off        Random Place H
  Sample Guy 1   7/20/2013 18:22  on         Random Place H
  Sample Guy 1   7/20/2013 18:24  off
  Sample Guy 2   8/1/2013 12:10   on         Random Place ZZ
  Sample Guy 2   8/1/2013 12:12   on         
  Sample Guy 2   8/1/2013 12:15   off        Random Place ZY
  Sample Guy 2   8/1/2013 13:10   on         Random Place ZY
  Sample Guy 2   8/1/2013 13:15   off
  </code></pre>
  
  <p>I'm trying to find the <strong>first</strong> ignition <em>off</em> point where landmark is Not Null, and the <strong>last</strong> ignition <em>on</em> point where landmark is Not Null for <strong>each day</strong>. Ideally, a calculated field for "duration" could be included to display the DateDiff between those two values.</p>
  
  <p><strong>Target Output:</strong></p>
  
  <pre><code>    vehicle        day          ignition   landmark  
  ---------------------------------------------------------
  Sample Guy 1   7/5/2013 15:10   off        Random Place B
  Sample Guy 1   7/5/2013 15:15   on         Random Place B
  Sample Guy 1   7/20/2013 18:20  off        Random Place H
  Sample Guy 1   7/20/2013 18:22  on         Random Place H
  Sample Guy 2   8/1/2013 12:15   off        Random Place ZY
  Sample Guy 2   8/1/2013 13:10   on         Random Place ZY
  </code></pre>
  
  <p>I understand this may be complex, but I'm looking to start understanding the building blocks to completing this.  Thanks everyone!</p>