Mysql中的递归层次查询（父子查询,无限极查询）

前言：最近面试的时候遇到公司要求只能用SQL来查询无限极的数据，不能用PHP程序做递归查询，现在分享方法。

下面给出一个​​function​​来完成的方法

下面是sql脚本，想要运行的直接赋值粘贴进数据库即可。

-- ---------------------------- 
-- Table structure for `treenodes` 
-- ---------------------------- 
DROP TABLE IF EXISTS `treenodes`; 
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;

-- ---------------------------- 
-- Records of treenodes 
-- ---------------------------- 
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');

把下面的语句直接粘贴进命令行执行即可（注意修改传入的参数，默认rootId，表明默认treenodes）

根据传入id查询所有父节点的id

方法1:

级数不知道，可以用类似下面这个语句查询, ​​@r := 6​​为查询条件

SELECT T2.id, T2.nodename, T2.pid
FROM ( 
    SELECT 
        @r AS _id, 
        (SELECT @r := pid FROM treenodes WHERE id = _id) AS pid, 
        @l := @l + 1 AS l
    FROM 
        (SELECT @r := 6, @l := 0) vars, 
        treenodes h 
    WHERE @r != 0) T1 
JOIN treenodes T2 
ON T1._id = T2.id 
ORDER BY T1.l;

结果:

方法2:

delimiter // 
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
//

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

delimiter // 
CREATE FUNCTION `getChildList`(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：