mysql实现oraclestartwithconnectby递归
在Oracle 中我们知道有⼀个 Hierarchical Queries 通过CONNECT BY 我们可以⽅便的查了所有当前节点下的所有⼦节点。但很遗憾，在MySQL的⽬前版本中还没有对应的功能。
在MySQL中如果是有限的层次，⽐如我们事先如果可以确定这个树的最⼤深度是4, 那么所有节点为根的树的深度均不会超过4，则我们可以直接通过left join 来实现。
但很多时候我们⽆法控制树的深度。这时就需要在MySQL中⽤存储过程来实现或在你的程序中来实现这个递归。本⽂讨论⼀下⼏种实现的⽅法。
样例数据：
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)
树形图如下
1:A
+-- 2:B
| +-- 4:D
| +-- 5:E
+-- 3:C
+-- 6:F
+-- 7:G
异步fifo核的调用设计8:H
+-- 9:I
| +-- 12:L
mysql语句转oracle| | +--14:N
| | +--15:O
| | +--16:P
| | +--17:Q
| +-- 13:M
+-- 10:J
+-- 11:K
⽅法⼀：利⽤函数来得到所有⼦节点号。
创建⼀个function getChildLst, 得到⼀个由所有⼦节点号组成的字符串.
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);
->
jsp倒计时代码-> 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 ;
使⽤我们直接利⽤find_in_set函数配合这个getChildlst来查
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)
优点: 简单，⽅便，没有递归调⽤层次深度的限制 (max_sp_recursion_depth，最⼤255) ；
缺点：长度受限，虽然可以扩⼤ RETURNS varchar(1000)，但总是有最⼤限制的。
MySQL⽬前版本( 5.1.33-community)中还不⽀持function 的递归调⽤。
⽅法⼆：利⽤临时表和过程递归
创建存储过程如下。createChildLst 为递归过程，showChildLst为调⽤⼊⼝过程，准备临时表及初始化。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 ;
调⽤时传⼊结点
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 |vmware官方下载
| 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)
depth 为深度，这样可以在程序进⾏⼀些显⽰上的格式化处理。类似于oracle中的 level 伪列。sno 仅供排序控制。这样你还可以通过临时表tmpLst与数据库中其它表进⾏联接查询。
MySQL中你可以利⽤系统参数 max_sp_recursion_depth 来控制递归调⽤的层数上限。如下例设为12.
mysql> set max_sp_recursion_depth=12;
Query OK, 0 rows affected (0.00 sec)
优点 : 可以更灵活处理，及层数的显⽰。并且可以按照树的遍历顺序得到结果。
缺点 : 递归有255的限制。
⽅法三：利⽤中间表和过程
(本⽅法由yongyupost2000提供样⼦改编)
创建存储过程如下。由于MySQL中不允许在同⼀语句中对临时表多次引⽤，只以使⽤普通表tmpLst来实现了。当然你的程序中负责在⽤完后清除这个表。
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);
执⾏完后会产⽣⼀个tmpLst表，nLevel 为节点深度，sCort 为排序字段。使⽤⽅法
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 |
linear是什么品牌| +--L |
| +--N |
| +--O |
安卓开发获取shell| +--P |
| +--Q |
| +--M |
+--------------------------------------------+
17 rows in set (0.00 sec)
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