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mysql 实现树形的遍历

前言：
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。

1、建立测试表和数据：

DROP TABLE IF EXISTS test.channel;
CREATE TABLE test.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);

2、用临时表和递归过程实现树的遍历（mysql的UDF不能递归调用）：

2.1、递归过程输出某节点id路径，类似Oracle SYS_CONNECT_BY_PATH的功能

-- 递归输出某节点id路径
DELIMITER //
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;
    -- 下面这行表示若没有数据返回，程序继续，并将变量done设为1
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
    -- mysql中可以利用系统参数 max_sp_recursion_depth 来控制递归调用的层数上限。
    SET max_sp_recursion_depth=12;

    OPEN cur1;
    -- 游标向下走一步
    FETCH cur1 INTO parentid,pathstr;
    WHILE done=0 DO
        CALL pro_cre_pathlist(parentid,delimit,pathstr);
        -- 游标向下走一步
        FETCH cur1 INTO parentid,pathstr;
    END WHILE;

    CLOSE cur1;
END //

DELIMITER ;

测试：

SET @str='16';
CALL pro_cre_pathlist(16,'/',@str);
SELECT @str;

测试结果：

2.2、递归过程输出某节点name路径

-- 递归输出某节点name路径
DELIMITER //
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;
    -- 下面这行表示若没有数据返回，程序继续，并将变量done设为1
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
    -- mysql中可以利用系统参数 max_sp_recursion_depth 来控制递归调用的层数上限。
    SET max_sp_recursion_depth=12;

    OPEN cur1;
    -- 游标向下走一步
    FETCH cur1 INTO parentid,pathstr;
    WHILE done=0 DO
        CALL pro_cre_pnlist(parentid,delimit,pathstr);
        -- 游标向下走一步
        FETCH cur1 INTO parentid,pathstr;
    END WHILE;

    CLOSE cur1;
END //

DELIMITER ;

测试：

SET @str='';
CALL pro_cre_pnlist(16,'/',@str);
SELECT @str;

测试结果：

2.3、调用函数输出id路径

-- 调用函数输出id路径
DELIMITER //
DROP FUNCTION IF EXISTS fn_tree_path;
CREATE FUNCTION fn_tree_path(nid INT,delimit VARCHAR(10)) 
RETURNS VARCHAR(2000) CHARSET utf8
BEGIN 
    DECLARE pathid VARCHAR(1000);
    
    SET pathid = CAST(nid AS CHAR);
    CALL pro_cre_pathlist(nid,delimit,pathid);
    
    RETURN pathid;
END //
DELIMITER ;

测试：

SELECT fn_tree_path(16,'/') AS id;

测试结果：

2.4、调用函数输出name路径

-- 调用函数输出name路径  
DELIMITER //
DROP FUNCTION IF EXISTS fn_tree_pathname;
CREATE FUNCTION fn_tree_pathname(nid INT,delimit VARCHAR(10)) 
RETURNS VARCHAR(2000) CHARSET utf8
BEGIN
    DECLARE pathid VARCHAR(1000);
    SET pathid='';
    CALL pro_cre_pnlist(nid,delimit,pathid);
    RETURN pathid;
END //
DELIMITER ;

测试：

SELECT fn_tree_pathname(16,'/') AS name;

测试结果：

2.5、调用过程输出子节点

-- 调用过程输出子节点   
DELIMITER //
DROP PROCEDURE IF EXISTS pro_show_childlist;
CREATE PROCEDURE pro_show_childlist(IN rootId INT)
BEGIN
    DROP TEMPORARY TABLE IF EXISTS tmpList;
    CREATE TEMPORARY TABLE IF NOT EXISTS tmpList(
        sno INT PRIMARY KEY AUTO_INCREMENT,
        id INT,
        depth INT);

    CALL pro_cre_childlist(rootId,0);

    SELECT channel.id,CONCAT(SPACE(tmpList.depth*2),'--',channel.cname)NAME,
    channel.parent_id,tmpList.depth,fn_tree_path(channel.id,'/')path,
    fn_tree_pathname(channel.id,'/')pathname FROM tmpList,channel 
    WHERE tmpList.id=channel.id ORDER BY tmpList.sno;
END //

DELIMITER ;

2.6、从某节点向下遍历子节点，递归生成临时表数据

DELIMITER //
DROP PROCEDURE IF EXISTS pro_cre_childlist;
CREATE PROCEDURE 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 tmpList 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 //

DELIMITER ;

2.7、调用过程输出父节点

-- 调用过程输出父节点   
DELIMITER //
DROP PROCEDURE IF EXISTS pro_show_parentlist;
CREATE PROCEDURE pro_show_parentlist(IN rootId INT)
BEGIN
    DROP TEMPORARY TABLE IF EXISTS tmpList;
    CREATE TEMPORARY TABLE IF NOT EXISTS tmpList(
        sno INT PRIMARY KEY AUTO_INCREMENT,
        id INT,
        depth INT);

    CALL pro_cre_parentlist(rootId,0);
    SELECT channel.id,CONCAT(SPACE(tmpList.depth*2),'--',channel.cname)NAME,
    channel.parent_id,tmpList.depth,fn_tree_path(channel.id,'/')path,
    fn_tree_pathname(channel.id,'/')pathname FROM tmpList,channel 
    WHERE tmpList.id=channel.id ORDER BY tmpList.sno;
END //

DELIMITER ;

2.8、从某节点向上追溯根节点，递归生成临时表数据

DELIMITER //
DROP PROCEDURE IF EXISTS pro_cre_parentlist;
CREATE PROCEDURE 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 tmpList 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 //

DELIMITER ;