title: How to query all the row that have different value for a same column
body: <p>I have a table opinions_answers with several columns, three of them interest me in this case <code>opinion_id</code> <code>date_answer</code> and <code>id_politician</code>.</p>
  
  <p>And I need to query all the row that have a specific opinion_id for which date_answer != "" and where <code>id_politician</code> is always different.</p>
  
  <p>I have this:</p>
  
  <pre><code>$this-&gt;db-&gt;from("opinions_answers");
  $this-&gt;db-&gt;where("opinion_id", 1);
  $this-&gt;db-&gt;where("date_answer !=", "");
  return $this-&gt;db-&gt;count_all_results();
  </code></pre>
  
  <p>It works but I don't know how to specify that the column <code>id_politician</code> must contain a different value in each row...</p>
  
  <p>Any idea?
  Thanks</p>