protected function execPre()
    {
        foreach ($this->preQueries as $pq) {
            if (is_array($pq)) {
                $pattern = $pq[0];
                $data = isset($pq[1]) ? $pq[1] : null;
            } else {
                $pattern = $pq;
                $data = null;
            }
            $this->query($pattern, $data);
        }
        $this->preQueries = array();
    }