title: Access Data Type Conversion to Boolean
body: <p>I am performing a query on the following table:</p>
  
  <p><b>Approval</b></p>
  
  <ul>
  <li>person (long int)</li>
  <li>item (long int)</li>
  <li>reason (long int)</li>
  <li>date (date)</li>
  <li>valid (bool)</li>
  </ul>
  
  <p>The first 3 fields are linked to other tables. Each person may have any number of entries in this table, for various items, reasons or dates. I then perform the following query:</p>
  
  <pre><code>SELECT Approval.person, 
          Approval.item,
          Approval.reason, 
          Min(Approval.valid) AS valid
  FROM Approval
  GROUP BY Approval.person, 
          Approval.item, 
          Approval.reason;
  </code></pre>
  
  <p>Why? Because I am not only interested in "<b>who</b> has <b>valid</b> status", but also "who ever had an approval for this item or reason, and is this approval still valid?"</p>
  
  <p>Now, this works - well, sort of. However, because I have performed a Minimum aggregate function, I have automatically changed the data-type from Yes/No to Numerical (I used the minimum aggregate function simply because I knew of no other better way to do it).</p>
  
  <p>So, the question is, how do I change the numbers -1 &amp; 0 back into a boolean value of True/False? Or, is there a better way of doing this query?</p>
  
  <p>Best regards,
  Phil</p>