如何更新cakephp 2.8.0中的字段

Question

我是Cakephp的新手（在2.8.0中工作），我想编辑字段（标签名）， 我有两个桌子

1) meta_description (id,tag_name,tag_image)
2) poll_meta(tag_id,poll_id)

我想如果tag_name（我发送的标签）已经存在，则不应保存新条目，否则应将新条目保存在meta_description中并用poll_id更新tag_id（我从视图发送） 现在我正在更新类别和内容，但是我也该如何更新标签名称？这是我的代码

 public function edit($id=null){
    //echo "here";exit;
    $this->layout='admin';
    if($this->Session->check('Auth.User')){
        if($this->Auth->User('role') == 'admin'){
            if (!$id) {
            $this->Session->setFlash('Please provide a user id');
            $this->redirect(array('action'=>'index'));
            }
            $category = $this->Poll->findById($id);

             $select = $this->PollCategory->find('first', array('fields' => array('category_id'), 'conditions' => array('poll_id' => $id)));
                $pc = $select['PollCategory']['category_id'];

        if ($this->request->is('post') || $this->request->is('put')) {
            $cat = $this->data['Poll']['category_id'];
            $this->Poll->id = $id;
            if ($this->Poll->save($this->request->data)) {

                $this->PollCategory->updateAll(array('category_id' => $cat),array('poll_id' => $id));

            $this->Session->setFlash($this->Success_alert(' The user has been updated.'), 'default', array(), 'success');
            $this->redirect(array('action' => 'index'));
            }else{

            $this->Session->setFlash($this->Error_alert(' Unable to update your user.'), 'default', array(), 'error');

            }
    }
        if (!$this->request->data) {
        $this->request->data = $category;
        }
        }else{
        $this->Session->setFlash($this->Error_alert(' Not Accessible. Log in As Administrator!'), 'default', array(), 'error');
        $this->redirect(array('controller' => 'users','action' => 'home'));
    }
}
 $pcategory = $this->Pcategory->find('list', array('fields' => array('id','name')));
             $this->set(compact('pcategory','pc',$pcategory,$pc));

}