这个是我在model文件里面写的一个方法。我想将一张表(t) 和 另一张表 c 做外连接(left join)。

    public function pagination($limit, $condition, $order){
        $criteria = new CDbCriteria();
        $criteria->alias = 't';
        $criteria->order = $order;
        $criteria->select = 't.id, c.value';
        $criteria->addCondition($condition);
        $criteria->join = 'left join lp_site_conf as c on t.type=c.id';
        $result['listInfo'] = YiiData($this->findAll($criteria));
        $result['pageCount'] = $pages->getPageCount();
    }

但是 现在查出来的数据是这样的

array(10) {
  [0] => array(9) {
    ["id"] => string(2) "10"
    ["name"] => NULL
    ["type"] => NULL
    ["createuid"] => NULL
    ["createtime"] => NULL
    ["modifytime"] => NULL
    ["description1"] => NULL
    ["description2"] => NULL
    ["status"] => NULL
  }
  [1] => array(9) {
    ["id"] => string(1) "9"
    ["name"] => NULL
    ["type"] => NULL
    ["createuid"] => NULL
    ["createtime"] => NULL
    ["modifytime"] => NULL
    ["description1"] => NULL
    ["description2"] => NULL
    ["status"] => NULL
  }

这些字段都是t表中的，根本没有leftjoin的表的字段，这是什么原因？