欅坂46

前言

       最近遇到了一个问题，在mysql中如何完成节点下的所有节点或节点上的所有父节点的查询？
在Oracle中我们知道有一个Hierarchical Queries可以通过CONNECT BY来查询，但是，在MySQL中还没有对应的函数!!!

创建数据表

下面是sql脚本，想要运行的直接赋值粘贴进数据库即可。

CREATE TABLE `treenodes` ( 
  `id` int(11) NOT NULL, 
  `nodename` varchar(20) DEFAULT NULL, 
  `pid` int(11) DEFAULT NULL, 
  PRIMARY KEY (`id`) 
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

插入几条数据

INSERT INTO `treenodes` VALUES ('1', 'A', '0'); 
INSERT INTO `treenodes` VALUES ('2', 'B', '1'); 
INSERT INTO `treenodes` VALUES ('3', 'C', '1'); 
INSERT INTO `treenodes` VALUES ('4', 'D', '2'); 
INSERT INTO `treenodes` VALUES ('5', 'E', '2'); 
INSERT INTO `treenodes` VALUES ('6', 'F', '3'); 
INSERT INTO `treenodes` VALUES ('7', 'G', '6'); 
INSERT INTO `treenodes` VALUES ('8', 'H', '0'); 
INSERT INTO `treenodes` VALUES ('9', 'I', '8'); 
INSERT INTO `treenodes` VALUES ('10', 'J', '8'); 
INSERT INTO `treenodes` VALUES ('11', 'K', '8'); 
INSERT INTO `treenodes` VALUES ('12', 'L', '9'); 
INSERT INTO `treenodes` VALUES ('13', 'M', '9'); 
INSERT INTO `treenodes` VALUES ('14', 'N', '12'); 
INSERT INTO `treenodes` VALUES ('15', 'O', '12'); 
INSERT INTO `treenodes` VALUES ('16', 'P', '15'); 
INSERT INTO `treenodes` VALUES ('17', 'Q', '15');

创建函数

根据传入id查询所有父节点的id

CREATE FUNCTION `getParLst`(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

执行命令

select * from treenodes where FIND_IN_SET(id,getParList(15));

结果

根据传入id查询所有子节点的id

CREATE FUNCTION `getParLst`(rootId INT)
RETURNS varchar(1000) 

BEGIN
    DECLARE sTemp VARCHAR(1000);
    DECLARE sTempChd VARCHAR(1000);

    SET sTemp = '$';
    SET sTempChd =cast(rootId as CHAR);

    WHILE sTempChd is not null DO
        SET sTemp = concat(sTemp,',',sTempChd);
        SELECT group_concat(id) INTO sTempChd FROM  treeNodes where FIND_IN_SET(pid,sTempChd)>0;
    END WHILE;
    RETURN sTemp; 
END

执行命令

select * from treenodes where FIND_IN_SET(id,getChildList(7));

结果

注意

如果返回数据量过多的话,设置的'varchar(1000)'是不够的,将返回类型改为 'mediumtext' 即可.