mysql> create table treeNodes
  -> (
  -> id int primary key,
  -> nodename varchar(20),
  -> pid int
  -> );
Query OK, 0 rows affected (0.09 sec)
mysql> select * from treenodes;
+----+----------+------+
| id | nodename | pid |
+----+----------+------+
| 1 | A    |  0 |
| 2 | B    |  1 |
| 3 | C    |  1 |
| 4 | D    |  2 |
| 5 | E    |  2 |
| 6 | F    |  3 |
| 7 | G    |  6 |
| 8 | H    |  0 |
| 9 | I    |  8 |
| 10 | J    |  8 |
| 11 | K    |  8 |
| 12 | L    |  9 |
| 13 | M    |  9 |
| 14 | N    |  12 |
| 15 | O    |  12 |
| 16 | P    |  15 |
| 17 | Q    |  15 |
+----+----------+------+
17 rows in set (0.00 sec)

 1:A
 +-- 2:B
 |  +-- 4:D
 |  +-- 5:E
 +-- 3:C
    +-- 6:F
      +-- 7:G
 8:H
 +-- 9:I
 |  +-- 12:L
 |  |  +--14:N
 |  |  +--15:O
 |  |    +--16:P
 |  |    +--17:Q
 |  +-- 13:M
 +-- 10:J
 +-- 11:K

mysql> delimiter //
mysql>
mysql> CREATE FUNCTION `getChildLst`(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
  -> //
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> delimiter ;

mysql> select getChildLst(1);
+-----------------+
| getChildLst(1) |
+-----------------+
| $,1,2,3,4,5,6,7 |
+-----------------+
1 row in set (0.00 sec)
mysql> select * from treeNodes
  -> where FIND_IN_SET(id, getChildLst(1));
+----+----------+------+
| id | nodename | pid |
+----+----------+------+
| 1 | A    |  0 |
| 2 | B    |  1 |
| 3 | C    |  1 |
| 4 | D    |  2 |
| 5 | E    |  2 |
| 6 | F    |  3 |
| 7 | G    |  6 |
+----+----------+------+
7 rows in set (0.01 sec)
mysql> select * from treeNodes
  -> where FIND_IN_SET(id, getChildLst(3));
+----+----------+------+
| id | nodename | pid |
+----+----------+------+
| 3 | C    |  1 |
| 6 | F    |  3 |
| 7 | G    |  6 |
+----+----------+------+
3 rows in set (0.01 sec)

mysql> delimiter //
mysql>
mysql> # 入口过程
mysql> CREATE PROCEDURE showChildLst (IN rootId INT)
  -> BEGIN
  -> CREATE TEMPORARY TABLE IF NOT EXISTS tmpLst
  ->  (sno int primary key auto_increment,id int,depth int);
  -> DELETE FROM tmpLst;
  ->
  -> CALL createChildLst(rootId,0);
  ->
  -> select tmpLst.*,treeNodes.* from tmpLst,treeNodes where tmpLst.id=treeNodes.id order by tmpLst.sno;
  -> END;
  -> //
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> # 递归过程
mysql> CREATE PROCEDURE createChildLst (IN rootId INT,IN nDepth INT)
  -> BEGIN
  -> DECLARE done INT DEFAULT 0;
  -> DECLARE b INT;
  -> DECLARE cur1 CURSOR FOR SELECT id FROM treeNodes where pid=rootId;
  -> DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
  ->
  -> insert into tmpLst values (null,rootId,nDepth);
  ->
  -> OPEN cur1;
  ->
  -> FETCH cur1 INTO b;
  -> WHILE done=0 DO
  ->     CALL createChildLst(b,nDepth+1);
  ->     FETCH cur1 INTO b;
  -> END WHILE;
  ->
  -> CLOSE cur1;
  -> END;
  -> //
Query OK, 0 rows affected (0.00 sec)
mysql> delimiter ;

mysql> call showChildLst(1);
+-----+------+-------+----+----------+------+
| sno | id  | depth | id | nodename | pid |
+-----+------+-------+----+----------+------+
|  4 |  1 |   0 | 1 | A    |  0 |
|  5 |  2 |   1 | 2 | B    |  1 |
|  6 |  4 |   2 | 4 | D    |  2 |
|  7 |  5 |   2 | 5 | E    |  2 |
|  8 |  3 |   1 | 3 | C    |  1 |
|  9 |  6 |   2 | 6 | F    |  3 |
| 10 |  7 |   3 | 7 | G    |  6 |
+-----+------+-------+----+----------+------+
7 rows in set (0.13 sec)
Query OK, 0 rows affected, 1 warning (0.14 sec)
mysql>
mysql> call showChildLst(3);
+-----+------+-------+----+----------+------+
| sno | id  | depth | id | nodename | pid |
+-----+------+-------+----+----------+------+
|  1 |  3 |   0 | 3 | C    |  1 |
|  2 |  6 |   1 | 6 | F    |  3 |
|  3 |  7 |   2 | 7 | G    |  6 |
+-----+------+-------+----+----------+------+
3 rows in set (0.11 sec)
Query OK, 0 rows affected, 1 warning (0.11 sec)

mysql> set max_sp_recursion_depth=12;
Query OK, 0 rows affected (0.00 sec)

delimiter //
drop PROCEDURE IF EXISTS showTreeNodes_yongyupost2000//
CREATE PROCEDURE showTreeNodes_yongyupost2000 (IN rootid INT)
BEGIN
 DECLARE Level int ;
 drop TABLE IF EXISTS tmpLst;
 CREATE TABLE tmpLst (
 id int,
 nLevel int,
 sCort varchar(8000)
 );
 Set Level=0 ;
 INSERT into tmpLst SELECT id,Level,ID FROM treeNodes WHERE PID=rootid;
 WHILE ROW_COUNT()>0 DO
 SET Level=Level+1 ;
 INSERT into tmpLst
  SELECT A.ID,Level,concat(B.sCort,A.ID) FROM treeNodes A,tmpLst B
  WHERE A.PID=B.ID AND B.nLevel=Level-1 ;
 END WHILE;
END;
//
delimiter ;
CALL showTreeNodes_yongyupost2000(0);

SELECT concat(SPACE(B.nLevel*2),'+--',A.nodename)
FROM treeNodes A,tmpLst B
WHERE A.ID=B.ID
ORDER BY B.sCort;
+--------------------------------------------+
| concat(SPACE(B.nLevel*2),'+--',A.nodename) |
+--------------------------------------------+
| +--A                    |
|  +--B                   |
|   +--D                  |
|   +--E                  |
|  +--C                   |
|   +--F                  |
|    +--G                 |
| +--H                    |
|  +--J                   |
|  +--K                   |
|  +--I                   |
|   +--L                  |
|    +--N                 |
|    +--O                 |
|     +--P                |
|     +--Q                |
|   +--M                  |
+--------------------------------------------+
17 rows in set (0.00 sec)