mysql递归查询。

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/*
Navicat MySQL Data Transfer

Source Server         : mysql_demo3
Source Server Version : 50521
Source Host           : localhost:3306
Source Database       : test

Target Server Type    : MYSQL
Target Server Version : 50521
File Encoding         : 65001

Date: 2012-09-02 21:16:03
*/

SET FOREIGN_KEY_CHECKS=0;

-- ----------------------------
-- 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');

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
如果给你一个这样的table，让你查询根节点为1下的所有节点记录（注意也包括根节点）？
可能有不少人想到connect by 函数，但是我灰常遗憾的告诉你，咱这儿是mysql！

解决方法：利用函数来得到所有子节点号。

闲话少续，看我的解决方法
创建一个function getChildLst, 得到一个由所有子节点号组成的字符串。
本文原始链接：http://www.jbxue.com/db/17554.html

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)

只要按我的做，百发百中弹无虚发，遇到问题万变不离其宗直接粘贴复制就是。

补充：
还可以做嵌套查询：

复制代码代码示例:select id,pid from treeNodes where id in(
     select id from treeNodes where FIND_IN_SET(id, getChildLst(3))
);

子查询的结果集是：
+--------+
id
----
3
6
7
+-------+
然后，经过外层查询就是：
id pid
3   1
6   3
6   6
---------

本文原始链接：http://www.jbxue.com/db/17554.html

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