mysql实现类似oracle的connect by功能

1.生成测试表与数据:
create table mytest
 (
  id int primary key,
  nodename varchar(20),
  pid int
 );
insert into mytest (id,nodename,pid)values(  1 ,‘A‘, 0);
insert into mytest (id,nodename,pid)values(  2 ,‘B‘, 1);
insert into mytest (id,nodename,pid)values(  3 ,‘C‘, 1);
insert into mytest (id,nodename,pid)values(  4 ,‘D‘, 2);
insert into mytest (id,nodename,pid)values(  5 ,‘E‘, 2);
insert into mytest (id,nodename,pid)values(  6 ,‘F‘, 3);
insert into mytest (id,nodename,pid)values(  7 ,‘G‘, 6);
insert into mytest (id,nodename,pid)values(  8 ,‘H‘, 0);
insert into mytest (id,nodename,pid)values(  9 ,‘I‘, 8);
insert into mytest (id,nodename,pid)values( 10 ,‘J‘, 8);
insert into mytest (id,nodename,pid)values( 11 ,‘K‘, 8);
insert into mytest (id,nodename,pid)values( 12 ,‘L‘, 9);
insert into mytest (id,nodename,pid)values( 13 ,‘M‘, 9);
insert into mytest (id,nodename,pid)values( 14 ,‘N‘,12);
insert into mytest (id,nodename,pid)values( 15 ,‘O‘,12);
insert into mytest (id,nodename,pid)values( 16 ,‘P‘,15);
insert into mytest (id,nodename,pid)values( 17 ,‘Q‘,15);

2.创建函数:
delimiter $$
CREATE FUNCTION `getParentList` (rootId VARCHAR (50)) RETURNS VARCHAR (1000)
 BEGIN
  DECLARE sParentList VARCHAR (1000) ;
  DECLARE sParentTemp VARCHAR(1000);
  SET sParentTemp =CAST(rootId AS CHAR);
  WHILE sParentTemp IS NOT NULL DO
  IF (sParentList IS NOT NULL) THEN
  SET sParentList = CONCAT(sParentTemp,‘/‘,sParentList);
  ELSE
  SET sParentList = CONCAT(sParentTemp);
  END IF;
 SELECT GROUP_CONCAT(pid) INTO sParentTemp FROM mytest WHERE FIND_IN_SET(id,sParentTemp)>0;
 END WHILE;
 RETURN sParentList;
 END$$
 DELIMITER ;

3.测试验证:
set global log_bin_trust_function_creators=1;
SELECT id,pid,getParentList(id) FROM mytest;

mysql> SELECT id,pid,getParentList(id) FROM mytest;
+----+------+-------------------+
| id | pid  | getParentList(id) |
+----+------+-------------------+
|  1 |    0 | 0/1               |
|  2 |    1 | 0/1/2             |
|  3 |    1 | 0/1/3             |
|  4 |    2 | 0/1/2/4           |
|  5 |    2 | 0/1/2/5           |
|  6 |    3 | 0/1/3/6           |
|  7 |    6 | 0/1/3/6/7         |
|  8 |    0 | 0/8               |
|  9 |    8 | 0/8/9             |
| 10 |    8 | 0/8/10            |
| 11 |    8 | 0/8/11            |
| 12 |    9 | 0/8/9/12          |
| 13 |    9 | 0/8/9/13          |
| 14 |   12 | 0/8/9/12/14       |
| 15 |   12 | 0/8/9/12/15       |
| 16 |   15 | 0/8/9/12/15/16    |
| 17 |   15 | 0/8/9/12/15/17    |
+----+------+-------------------+
17 rows in set (0.01 sec)