If you are getting this error below after moving your Drupal folder to another subfolder and somehow drupal is still referring to the old path see the solution below:
Error:
"Fatal error: require_once(): Failed opening required '/XXX/includes/database/query.inc' (include_path='.:/usr/share/php:/usr/share/php/zend') in /XXX/includes/database/select.inc on line 8
Solution:
Restart Apache