title: I got this message (CANNOT_GROUP_WITHOUT_AGG) from a simple query
body: <p>I how to fix this error message?</p>
  
  <p><code>Unable to parse query string for Function QUERY parameter 2: 
  CANNOT_GROUP_WITHOUT_AGG</code></p>
  
  <p>I got that error message just from a simple query formula, I already tried to search about it and try with the curly bracket <code>{ ... }</code> but it doesn't fixed,
  Can anyone help me or ever experienced it?</p>
  
  <pre><code>=QUERY(ANSWER!C:C, "SELECT * GROUP BY C", 0)
  </code></pre>