title: mysql 1054 error "unknown column" in "on clause"... but the column IS there
body: <p>OK, I'm pulling my hair out on this one.  I've simplified my select statement down a bit on this:</p>
  
  <pre><code>SELECT xmatterspagetask.id pagetaskid, xmpurpose.purposetext
  FROM xmatterspagetask
  LEFT OUTER JOIN xmpurpose on (xmatterspagetask.purpose_id = xmpurpose.id)
  </code></pre>
  
  <blockquote>
    <p>#1054 - Unknown column 'xmpurpose.id' in 'on clause'</p>
  </blockquote>
  
  <p>The xmpurpose table does exist.  It only has two columns, id and purposetext.  It's intended to be a reference table. </p>
  
  <p>I have other very similar two-column reference tables in the full-blown version of this query.   Doing LEFT OUTER JOINs to them works just fine.   Can't figure out why I'm blowing-up on this one.</p>
  
  <p>Any thoughts?</p>
  
  <p>Thanks!</p>