title: Access query to include all values, including Null
body: <p>I have a query that is being generated from a single table. Using the form to set criteria for my query I'm running into issues with null values. I'll simplify my issue below.</p>
  
  <p><strong>The Table</strong> [Permits]
  The table is called Permits.  There is one field that I would like to filter which is called Status.  Within the Status field there are the following entries: null values,"completed" and "Cancelled." Essentially, the null values indicate that a permit status is open.</p>
  
  <p><strong>In the Form:</strong> [FormQuery]
  The form is called FormQuery and has check boxes that will allow a user to select the criteria for their query.  The form has four check boxes with the names: all, completed, open, cancelled.</p>
  
  <p><strong>In the query:</strong> filtering through [Permits]![Status]
  There are a number of fields in the query.  The only field with critera is (Permits.Status).The following criteria is entered:</p>
  
  <pre><code>In (IIf([Forms]![FormQuery]![Completed]=True,"COMPLETED",""),
      IIf([Forms]![FormQuery]![Cancelled]=True,"Cancelled",""),
      IIf([Forms]![FormQuery]![All]=True,[Permits]![Status],""))
  </code></pre>
  
  <p>As I understand it <code>IN(...)</code> is setting a list of criteria.  The criteria are dependent on the form checks as seen in the <code>[Forms]![FormQuery]![Completed]=true</code> section. If the box is checked, a string is passed, otherwise is a "" null value. So when just completed is checked off the list looks like <code>In (completed)</code></p>
  
  <p>The form works.  When I have the "completed" check box selected the query will bring up all completed.  It works similarly with the cancelled and with the all check box.  The one issue is that the code found on the last line, especially the part <code>[permits]![status]</code> is only bringing up entries that are populated and null values are being missed. </p>
  
  <p>How would I search for nulls and how would I include nulls in the all query? </p>
  
  <p>Any help would be greatly appreciated.</p>