public function findAll()
    {
        // convert to condition.
        $cond = call_user_func_array(array($this, 'toCondition'), func_get_args());

        // to SQL.
        $sql = $cond->toSQL();
        var_dump($sql, $cond->getParams());

        // query.
        $sth = $this->query($sql, $cond->getParams());
        $entities = new Entities($this, $sth);
        return $entities;
    }