title: Mysql query does not work, displays an empty field
body: <p>The first table with posts (posts with columns: id, post_id, post_name, post_date)</p>
  
  <p>The second table with a view counter (post_views with columns: id, post_id, post_views).</p>
  
  <pre class="lang-php prettyprint-override"><code>$count_boards = $db-&gt; super_query ("SELECT * FROM posts AS p
  JOIN post_views AS pv ON p.post_id = pv.post_id
  WHERE p.post_date&gt; = (CURDATE () - INTERVAL 3 DAY) ";
  
  $count_boards = $count_boards['post_views'];
  echo $count_boards;
  </code></pre>
  
  <p>When outputting, it doesn’t output anything, that is, it is empty ... What could be the problem?</p>