public function count($field='*')
    {
        $this->getQuery()->type('select')->remove('fields')->set('count', $field);
        
        $result = $this->query();
        
        if ($result) {// get first row's value
            $result = current($result[0]);
        } else {
            $result = 0;
        }
        
        return $result;
    }