以前一直使用父子无限分类，这种分类结构清晰，使用也简单。但若分类数量很大的话，在查询上性能不佳。比如在做导航菜单中，我要根据某一分类查询出整个分类树的话（祖辈）。
性能消耗是非常大的，要么做递归，要么做多次查询。故，对于分类的数据量很大的情况，我推荐使用左右值，以减少查询上的麻烦。
复制代码 代码如下:
_id
    /**
         +----------------------------------------------------------
         * 构造函数
         * @access public
         * @return void
         +----------------------------------------------------------
         */
    public  function __construct($left,$right,$id){
        parent::__construct();
       $this->_left = $left;
       $this->_right = $right;
       $this->_id = $id;
    }
    /**
      +----------------------------------------------------------
      * 根据node$this->_id得到该node的所有值
      * @access public
      * @param $nodeId
      * @return array
      +----------------------------------------------------------
     */    
    public  function getNodeById($nodeId)
    {
        if($nodeId>0)
        {
            return $this->getById($nodeId);
        }
        else
        {
            throw_exception('未知$this->_id');
            return false;
        }
    }
    /**
           +----------------------------------------------------------
           * 获取父节点,含直属父类（type=1），所有父类：type=0
           * @access public
           * @param $nodeId int 节点$this->_id
           * @return $parentNode array()
           +----------------------------------------------------------
          */    
    public  function getParentNode($nodeId,$type = 0)
    {
        if($nodeId == 0) throw_exception('未知$this->_id');;
        $currentNode = $this->getNodeById($nodeId);
        if($currentNode)
        {
            $condition = " ".$this->_left.'<'.$currentNode[$this->_left].' and '.$this->_right.' >'.$currentNode[$this->_right]." ";
            if($type ==1) //直属父类
            {
                return $this->where($condition)->order($this->_left." DESC")->limit(1)->find();
                //                $sql = "SELECT * FROM ".TABLE_NAME." WHERE {$condition} ORDER BY ".$this->_left." DESC LIMIT 1";
                //                return mysql_query($sql) or die(mysql_error());
            }
            else if($type ==0)
            {
                return $this->where($condition)->findAll();
                //                $sql = "SELECT * FROM ".TABLE_NAME." WHERE {$condition} ";
                //                return mysql_query($sql) or die(mysql_error());
            }
        }
        else
        {
            return false;
        }
    }
    /**
         +----------------------------------------------------------
         * 当前节点下子孙节点总数.子孙总数＝（当前节点的右值 - 当前节点的左值-1）/2
         * @access public
         * @param $node_id int 节点$this->_id
         * @return $amount int 该节点下的子孙总数         *
         +----------------------------------------------------------
         */
    public  function getChildCount($nodeId)
    {
        $currentNode = $this->getNodeById($nodeId);
        if(!empty($currentNode))
        {
            return (int)($currentNode[$this->_right]-$currentNode[$this->_left] -1)/2;
        }
    }
    /**
      +----------------------------------------------------------
      * 获取当前节点下所有子节点。 当 A子类的右节点=B子类左节点-1 则 A、B属于同一级别
      * @access public
      * @param $curentId
      * @param  $type int 0：当前节点下所有子类，1为当前节点下一级子类
      * @return bool
      +----------------------------------------------------------
     */    
    public  function getChild($nodeId,$type=0)
    {
        $currentNode = $this->getNodeById($nodeId);
        if($currentNode[$this->_left]-$currentNode[$this->_right] ==1)
        {
            return false; //当 该节点左值 - 右值=1  时，其下没有子节点。
        }
        else
        {
            $condition = $this->_left.'>'.$currentNode[$this->_left].' and '.$this->_right .'<'.$currentNode[$this->_right];
            $child = $this->where($condition)->findAll();
            if($type == 0)//所有子类
            {
                return $child;
            }
            else if($type ==1) //获取当前节点下一级分类
            {                       
                $subArr = array(); //一级子类
                foreach ($child as $k=>$sub) {
                    //子类的左节点=父类左节点+1，则子类为第一个子类
                    if($sub[$this->_left]==$currentNode[$this->_left]+1)
                    {
                        //$right = $sub[$k][$this->_right]; //当前节点的右节点
                        $firstSub = $sub; //当前节点下第一个子类
                        array_push($subArr,$firstSub); //子类入栈
                        unset($child[$k]);
                    }
                }
                $rightVal =  $firstSub[$this->_right]; //第一个子节点为比较标志
                $childCount = count($child);//剩余子节点数
                for($i=0;$i<$childCount;$i++) //循环检索出 同级子节点
                {
                    foreach ($child as $key => $sub2) {
                        if($rightVal == $sub2[$this->_left]-1)
                        {
                            $rightVal = $sub2[$this->_right]; //把循环当前的node的右节点当做比较值
                            array_push($subArr,$sub2);
                            unset($child[$key]);
                        }
                    }
                }
                return $subArr;
            }
        }
    }
    /**
         +----------------------------------------------------------
         * 返回当前节点的完整路径
         * @access public
         * @param $nodeId
         * @return array
         +----------------------------------------------------------
        */    
    public  function getSinglePath($nodeId)
    {
        $sql = "select parent.* from __TABLE__ as node,__TABLE__ as parent where node.{$this->_left} between parent.{$this->_left}
            AND parent.{$this->_right} AND node.{$this->_id} = {$nodeId} order by parent.{$this->_left}";
//        echo $sql;
        return $this->query($sql);
    }
    /**
      +----------------------------------------------------------
      * 添加子节点，分3种：0：在当前节点下最后追加一个子节点；1：在当前节点下追加第一个子节点；

2：在当前节点下的某个子节点后追加
复制代码 代码如下:
      * @access public
      * @param $currentId int
      * @param $nodeName string 新节点名称     
      * @param $targetId int 追加到当前节点下子节点的指定节点后
      * @return bool
      +----------------------------------------------------------
     */   
    public  function addNode($nodeId,$newData,$type=0,$targetId=0)
    {
        if(empty($newData))
        {
            throw_exception('新分类不能为空');
        }
        $currentNode = $this->getNodeById($nodeId);
        switch ($type) {
            case 0:
                $leftNode  = $currentNode[$this->_right]; //新节点的左值为父节点的右值
                $rightNode = $leftNode+1;
                break;
            case 1:
                $leftNode = $currentNode[$this->_left]+1; //新节点的左值为父节点的左值+1
                $rightNode = $leftNode+1;
                break;
            case 2:
                $otherNode = $this->getNodeById($targetId);
                $leftNode = $otherNode[$this->_right]+1;
                $rightNode = $leftNode+1;
            default:
                break;
        }
//         $sql = "UPDATE ".TABLE_NAME." SET ".$this->_right."=".$this->_right."+2 WHERE ".$this->_right." >= ".$leftNode;
//        $sql2 = "UPDATE ".TABLE_NAME." SET ".$this->_left."=".$this->_left."+2 WHERE ".$this->_left.">".$leftNode;
        $this->setInc($this->_right,$this->_right.">=".$leftNode,2); //把所有右值大于新节点左值的节点的右值+2,注意效率
        $this->setInc($this->_left,$this->_left.">".$leftNode,2);   //把所有大于新节点的左值+2
        $newData[$this->_left] = (int)$leftNode;
        $newData[$this->_right] =(int) $rightNode;
        return $this->add($newData);
    }
    /**
         +----------------------------------------------------------
         * 删除节点
         * @access public
         * @param type 操作类型，默认为0删除当前节点下的所有子节点，1为删除包括自身的节点
         * @param $nodeId int 要删除的$this->_id
         * @return bool
         +----------------------------------------------------------
        */    
    public  function rmNode($nodeId,$type =1)
    {
        $currentNode = $this->getNodeById($nodeId);
        if($type == 1) //删除包含自身的节点
        {
            $sql = "DELETE FROM __TABLE__ WHERE ".$this->_left.">= {$currentNode[$this->_left]} AND ".$this->_right."<= {$currentNode[$this->_right]}";
            $childCount = ($this->getChildCount($nodeId)+1)*2; //要更新的值
            $sql2 = "UPDATE  __TABLE__  SET ".$this->_right."=".$this->_right."-".$childCount." WHERE ".$this->_right.">".$currentNode[$this->_right];
            $sql3 = "UPDATE  __TABLE__  SET ".$this->_left."=".$this->_left."-".$childCount." WHERE ".$this->_left.">".$currentNode[$this->_left];
        }
        else //删除当前节点下的所有节点
        {
            $sql ="DELETE FROM __TABLE__ WHERE ".$this->_left."> {$currentNode[$this->_left]} AND ".$this->_right."< {$currentNode[$this->_right]}";
            $childCount = $this->getChildCount($nodeId)*2; //要更新的值
            $sql2 = "UPDATE __TABLE__ SET ".$this->_right."=".$this->_right ."-".$childCount." WHERE ".$this->_right.">=".$currentNode[$this->_right];
            $sql3 = "UPDATE __TABLE__ SET ".$this->_left."=".$this->_left."-".$childCount." WHERE ".$this->_left.">".$currentNode[$this->_left];
        }
         $this->execute($sql); 
         $this->execute($sql2); 
         $this->execute($sql3); 
        return true;
    }
     /**
      +----------------------------------------------------------
      * 修改节点，名称等
      * @access public
      * @param $newData array()必须含有 要修改的$this->_id,k-v必须对齐，如arr['node_name'] = '商品'
      * @return bool
      +----------------------------------------------------------
     */    
    public  function modiNode($newData)
       {
            if(!empty($newData))
            {
                $id = $newData[$this->_id];               
                unset($newData[$this->_id]);
                return $this->save($newData,$this->_id.'='.$id);                              
          }
       }
}
?>