/**
* Get descendant ids.
*
* @param competency $competency The competency.
* @return array Array of competencies ids.
*/
public static function get_descendants_ids($competency)
{
global $DB;
$path = $DB->sql_like_escape($competency->get_path() . $competency->get_id() . '/') . '%';
$like = $DB->sql_like('path', ':likepath');
return $DB->get_fieldset_select(self::TABLE, 'id', $like, array('likepath' => $path));
}