? ? ? ? 关于多级别菜单栏或者权限系统中部门上下级的树形遍历，oracle中有connect by来实现， mysql没有这样的便捷途径，所以MySQL遍历数据表是我们经常会遇到的头痛问题，下面通过存储过程来实现。

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1，建立测试表和数据：

DROP TABLE IF EXISTS csdn.channel;   
CREATE TABLE csdn.channel (   
  id INT(11) NOT NULL AUTO_INCREMENT,     
  cname VARCHAR(200) DEFAULT NULL,   
  parent_id INT(11) DEFAULT NULL,   
  PRIMARY KEY (id)   
) ENGINE=INNODB DEFAULT CHARSET=utf8;   
INSERT  INTO channel(id,cname,parent_id)    
VALUES (13,‘首页‘,-1),   
       (14,‘TV580‘,-1),   
       (15,‘生活580‘,-1),   
       (16,‘左上幻灯片‘,13),   
       (17,‘帮忙‘,14),   
       (18,‘栏目简介‘,17);  
DROP TABLE IF EXISTS channel;

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2，利用临时表和递归过程实现树的遍历（mysql的UDF不能递归调用）：

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2.1，从某节点向下遍历子节点，递归生成临时表数据 ?

-- pro_cre_childlist
DELIMITER $$     
DROP PROCEDURE IF EXISTS csdn.pro_cre_childlist$$   
CREATE PROCEDURE csdn.pro_cre_childlist(IN rootId INT,IN nDepth INT)   
BEGIN   
      DECLARE done INT DEFAULT 0;   
      DECLARE b INT;   
      DECLARE cur1 CURSOR FOR SELECT id FROM channel WHERE parent_id=rootId;   
      DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;   
      SET max_sp_recursion_depth=12;   
       
      INSERT INTO tmpLst VALUES (NULL,rootId,nDepth);   
       
      OPEN cur1;   
       
      FETCH cur1 INTO b;   
      WHILE done=0 DO   
              CALL pro_cre_childlist(b,nDepth+1);   
              FETCH cur1 INTO b;   
      END WHILE;   
       
      CLOSE cur1;   
END$$   

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2.2，从某节点向上追溯根节点，递归生成临时表数据 ?

-- pro_cre_parentlist
DELIMITER $$
DROP PROCEDURE IF EXISTS csdn.pro_cre_parentlist$$   
CREATE PROCEDURE csdn.pro_cre_parentlist(IN rootId INT,IN nDepth INT)   
BEGIN   
      DECLARE done INT DEFAULT 0;   
      DECLARE b INT;   
      DECLARE cur1 CURSOR FOR SELECT parent_id FROM channel WHERE id=rootId;   
      DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;   
      SET max_sp_recursion_depth=12;   
       
      INSERT INTO tmpLst VALUES (NULL,rootId,nDepth);   
       
      OPEN cur1;   
       
      FETCH cur1 INTO b;   
      WHILE done=0 DO   
              CALL pro_cre_parentlist(b,nDepth+1);   
              FETCH cur1 INTO b;   
      END WHILE;   
       
      CLOSE cur1;   
     END$$   

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2.3，实现类似 Oracle SYS_CONNECT_BY_PATH的功能，递归过程输出某节点id路径 ?

-- pro_cre_pathlist
DELIMITER $$
USE csdn$$
DROP PROCEDURE IF EXISTS pro_cre_pathlist$$
CREATE PROCEDURE pro_cre_pathlist(IN nid INT,IN delimit VARCHAR(10),INOUT pathstr VARCHAR(1000))
BEGIN                     
      DECLARE done INT DEFAULT 0;   
      DECLARE parentid INT DEFAULT 0;         
      DECLARE cur1 CURSOR FOR    
      SELECT t.parent_id,CONCAT(CAST(t.parent_id AS CHAR),delimit,pathstr)   
        FROM channel AS t WHERE t.id = nid;   
           
      DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;   
      SET max_sp_recursion_depth=12;                     
       
      OPEN cur1;   
       
      FETCH cur1 INTO parentid,pathstr;   
      WHILE done=0 DO              
              CALL pro_cre_pathlist(parentid,delimit,pathstr);   
              FETCH cur1 INTO parentid,pathstr;   
      END WHILE;   
            
      CLOSE cur1;    
END$$


DELIMITER ;

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2.4，递归过程输出某节点name路径 ?

-- pro_cre_pnlist
DELIMITER $$
USE csdn$$
DROP PROCEDURE IF EXISTS pro_cre_pnlist$$
CREATE PROCEDURE pro_cre_pnlist(IN nid INT,IN delimit VARCHAR(10),INOUT pathstr VARCHAR(1000))
BEGIN                     
      DECLARE done INT DEFAULT 0;   
      DECLARE parentid INT DEFAULT 0;         
      DECLARE cur1 CURSOR FOR    
      SELECT t.parent_id,CONCAT(t.cname,delimit,pathstr)   
        FROM channel AS t WHERE t.id = nid;   
           
      DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;   
      SET max_sp_recursion_depth=12;                     
       
      OPEN cur1;   
       
      FETCH cur1 INTO parentid,pathstr;   
      WHILE done=0 DO              
              CALL pro_cre_pnlist(parentid,delimit,pathstr);   
              FETCH cur1 INTO parentid,pathstr;   
      END WHILE;   
            
      CLOSE cur1;    
     END$$


DELIMITER ;

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