mysql家谱表查询某人所有后代

CREATE TABLE `people` (
 `id` INT(11) NOT NULL,
 `name` VARCHAR(50) NULL DEFAULT NULL,
 `pid` INT(11) NOT NULL DEFAULT '0',
 PRIMARY KEY (`id`)
);
 
CREATE DEFINER=`root`@`%` PROCEDURE `getChildren`(IN `parentId` INT)
 LANGUAGE SQL
 NOT DETERMINISTIC
 CONTAINS SQL
 SQL SECURITY DEFINER
 COMMENT '获取某人所有后代'
BEGIN
 #存放结果的临时表
 DROP TABLE IF EXISTS children;
 CREATE TEMPORARY TABLE children SELECT 0 pLevel,p.* FROM `people` p WHERE id=parentId;
 #存放中间结果的临时表
 DROP TABLE IF EXISTS tem;
 CREATE TEMPORARY TABLE tem SELECT id FROM `people` limit 0;
 
 #逐级填充后代
 SET @pLevel=1;
 REPEAT
 #清空上次数据
 TRUNCATE TABLE tem;
 #将当前level的后代id放入临时表
 INSERT INTO tem SELECT p.id FROM `people` P, children c 
 WHERE p.pid=c.id AND c.pLevel=(@pLevel-1);
 #将当前level的后代数据塞入结果临时表
 INSERT INTO children SELECT @pLevel pLevel,p.* FROM `people` p, tem t 
 WHERE p.id=t.id;
 SET @pLevel=@pLevel+1;
 UNTIL NOT EXISTS (SELECT * FROM tem) OR @pLevel > 10
 END REPEAT;
 
 #调整表结构，删除临时列和不需要的数据
 ALTER TABLE children DROP COLUMN pLevel;
 DELETE FROM children WHERE id=parentId;
 
 #返回结果
 SELECT * from children;
END