title: Disjunction between tables that always dont exist
body: <p>I have mapped K and Other to a parent table Errand and they are related true an id, the thing is the Errand only has one K or one Other never both! When I have a Crieteria Query on only one row like this is works seamlessly;</p>
  
  <pre><code>    public void AddNoteQuery(DetachedCriteria query)
      {
          if (_request.Note != null)
          {
              query
                  .CreateAlias("Other", "o")
                  .Add(Restrictions.Eq("o.Note", _request.Note));
          }
      }
  </code></pre>
  
  <p>But when I try to do an K OR Other Criteria Query I get no results!</p>
  
  <pre><code>    public void AddNoteQuery(DetachedCriteria query)
      {
          if (_request.Note != null)
          {
              query
                  .CreateAlias("K", "k")
                  .CreateAlias("Other", "o")
                  .Add(Restrictions.Or(
                      Restrictions.Eq("k.Note", _request.Note),
                      Restrictions.Eq("o.Note", _request.Note)));
          }
      }
  </code></pre>