title: Each GROUP BY expression must contain at least one column that is not an outer reference. 13
body: <pre><code>SELECT NumberOfUsers,'date' AS Date
  FROM son.LicenseUsageStats
  GROUP BY 'date'
  </code></pre>
  
  <p>table includes 4 columns</p>
  
  <pre><code>rownum | numberofusers | timestamp | date
  </code></pre>
  
  <p>table logs number of users every hour so each day there are several entries</p>
  
  <p>attempting to capture number of users by month and getting error </p>
  
  <blockquote>
    <p>"Each GROUP BY expression must contain at least one column that is not an outer reference."</p>
  </blockquote>