Mysql递归获取某个父节点下面的所有子节点和子节点上的所有父节点

在MySQL中自定义函数来实现递归获取所有子节点，该方式的优点是可以减少java代码量，缺点是：1.不好维护；2.拼接的字段太长的时候，自定义函数的返回值可能容量不够，此时可以定义为text等大容量类型；3：show variables like 'group_concat_max_len'  查看group_concat的容量为1024 ，具体内容查看：https://blog.csdn.net/world_ding/article/details/54286862
。还有一个注意点,在生产环境中要给自定义的函数分配权限，不然可能会没有权限请求这个自定义的函数。

1.MySQL表结构和数据

/*
Navicat MySQL Data Transfer

Source Server         : localhost_3306
Source Server Version : 50712
Source Host           : localhost:3306
Source Database       : test

Target Server Type    : MYSQL
Target Server Version : 50712
File Encoding         : 65001

Date: 2018-04-13 12:47:42
*/

SET FOREIGN_KEY_CHECKS=0;

-- ----------------------------
-- Table structure for treenodes
-- ----------------------------
DROP TABLE IF EXISTS `treenodes`;
CREATE TABLE `treenodes` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `nodename` varchar(50) DEFAULT NULL,
  `pid` int(11) DEFAULT '0',
  `text` text,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=26 DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of treenodes
-- ----------------------------
INSERT INTO `treenodes` VALUES ('1', 'A', '0', null);
INSERT INTO `treenodes` VALUES ('2', 'B', '1', null);
INSERT INTO `treenodes` VALUES ('3', 'C', '1', null);
INSERT INTO `treenodes` VALUES ('4', 'D', '2', null);
INSERT INTO `treenodes` VALUES ('5', 'E', '2', null);
INSERT INTO `treenodes` VALUES ('6', 'F', '3', null);
INSERT INTO `treenodes` VALUES ('7', 'G', '6', null);
INSERT INTO `treenodes` VALUES ('8', 'H', '0', null);
INSERT INTO `treenodes` VALUES ('9', 'I', '8', null);
INSERT INTO `treenodes` VALUES ('10', 'J', '8', null);
INSERT INTO `treenodes` VALUES ('11', 'K', '8', null);
INSERT INTO `treenodes` VALUES ('12', 'L', '9', null);
INSERT INTO `treenodes` VALUES ('13', 'M', '9', null);
INSERT INTO `treenodes` VALUES ('14', 'N', '12', null);
INSERT INTO `treenodes` VALUES ('15', 'O', '12', null);
INSERT INTO `treenodes` VALUES ('16', 'P', '15', null);
INSERT INTO `treenodes` VALUES ('17', 'Q', '15', null);
INSERT INTO `treenodes` VALUES ('18', '一级机构', '7', null);
INSERT INTO `treenodes` VALUES ('19', '二级机构', '18', null);
INSERT INTO `treenodes` VALUES ('20', '三级机构', '19', null);
INSERT INTO `treenodes` VALUES ('21', '销售经理', '20', null);
INSERT INTO `treenodes` VALUES ('22', '销售经理2', '21', null);
INSERT INTO `treenodes` VALUES ('23', '代理人', '22', null);
INSERT INTO `treenodes` VALUES ('24', '代理人', '22', null);
INSERT INTO `treenodes` VALUES ('25', '不该出现', null, null);

2.自定义获取某个父节点下面的所有子节点的函数

CREATE FUNCTION `getChildList`(rootId INT)
RETURNS varchar(1000) 
 
BEGIN
	  #声明两个局部变量
    DECLARE sTemp VARCHAR(1000);
    DECLARE sTempChd VARCHAR(1000);
		#初始化局部变量
    SET sTemp = '$';
		#调用cast函数将int转换为char
    SET sTempChd =cast(rootId as CHAR);
    #递归拼接
    WHILE sTempChd is not null DO
				#存储每次递归结果
        SET sTemp = concat(sTemp,',',sTempChd);
				#将参数作为pid，然后查询其子id，然后将子id作为pid，
        #查询以子id为pid的子id，依次循环下去，直到所有节点都为叶子节点
        SELECT group_concat(id) INTO sTempChd FROM  treeNodes where FIND_IN_SET(pid,sTempChd)>0;
    END WHILE;
    RETURN sTemp; 
END



#测试
select * from treenodes where FIND_IN_SET(id,getChildList(20));

3.自定义获取子节点上的所有父节点函数

CREATE FUNCTION `getParList`(rootId INT)
RETURNS varchar(1000) 
BEGIN
    DECLARE sTemp VARCHAR(1000);
    DECLARE sTempPar VARCHAR(1000); 
    SET sTemp = ''; 
    SET sTempPar =rootId; 
 
    #循环递归
    WHILE sTempPar is not null DO 
        #判断是否是第一个，不加的话第一个会为空
        IF sTemp != '' THEN
            SET sTemp = concat(sTemp,',',sTempPar);
        ELSE
            SET sTemp = sTempPar;
        END IF;
        SET sTemp = concat(sTemp,',',sTempPar); 
        SELECT group_concat(pid) INTO sTempPar FROM treenodes where pid<>id and FIND_IN_SET(id,sTempPar)>0; 
    END WHILE; 
 
RETURN sTemp; 
END
#测试
select * from treenodes where FIND_IN_SET(id,getParList(15));

4.删除自定义的函数

DROP FUNCTION `getChildList`;