algorithm - 递归查询邻接表以在 SQL 中预先排序树遍历？

Question

我正在将数据从一个数据库架构迁移到另一个数据库架构。老人schema 有一个基于邻接表的分类系统，ID、类别和 parent_id。如果一个类别低于一秒，那类别将第二个 ID 作为其父 ID。例如:

+-------------+----------------------+--------+
| category_id | name                 | parent |
+-------------+----------------------+--------+
|           1 | ELECTRONICS          |   NULL |
|           2 | TELEVISIONS          |      1 |
|           3 | TUBE                 |      2 |
|           4 | LCD                  |      2 |
|           5 | PLASMA               |      2 |
|           6 | PORTABLE ELECTRONICS |      1 |
|           7 | MP3 PLAYERS          |      6 |
|           8 | FLASH                |      7 |
|           9 | CD PLAYERS           |      6 |
|          10 | 2 WAY RADIOS         |      6 |
+-------------+----------------------+--------+

新模式有一个改进的前序树遍历算法:

+-------------+----------------------+-----+-----+
| category_id | name                 | lft | rgt |
+-------------+----------------------+-----+-----+
|           1 | ELECTRONICS          |   1 |  20 |
|           2 | TELEVISIONS          |   2 |   9 |
|           3 | TUBE                 |   3 |   4 |
|           4 | LCD                  |   5 |   6 |
|           5 | PLASMA               |   7 |   8 |
|           6 | PORTABLE ELECTRONICS |  10 |  19 |
|           7 | MP3 PLAYERS          |  11 |  14 |
|           8 | FLASH                |  12 |  13 |
|           9 | CD PLAYERS           |  15 |  16 |
|          10 | 2 WAY RADIOS         |  17 |  18 |
+-------------+----------------------+-----+-----+

示例取自文章 Managing Hierarchical Data in MySQL .

无论如何，我有能力或编写具有递归函数的 php 脚本这会将邻接表迁移到预序树结构。基本上对于每一行，它都会插入一个空白的“rgt”值，看起来对于 child ，将函数递归地应用于他们，保持跟踪计数器的值，然后更新 'rgt' 值。

但我想在纯 SQL 中执行此操作。但是，我所知道的还不够一个立足点。对于初学者，我不知道你是否可以用递归查询，或者是否有其他方法可以做到这一点。

Answer 1

这是我得到的；这是一个示例，可以推广或适应您的情况。

首先我会建立一个邻接表(来自维基百科的语言家族数据):

CREATE TABLE IF NOT EXISTS `language_family_adj_list` (
  `language_id` int(11) NOT NULL auto_increment,
  `language` varchar(20) NOT NULL,
  `parent_id` int(11) default NULL,
  PRIMARY KEY  (`language_id`)
) ENGINE=MyISAM  DEFAULT CHARSET=utf8 AUTO_INCREMENT=41 ;


INSERT INTO `language_family_adj_list` (`language_id`, `language`, `parent_id`) VALUES
(1, 'Finno-Ugric', NULL),
(2, 'Hungarian', 1),
(3, 'Khanty', 1),
(4, 'Mansi', 1),
(5, 'Permic', 1),
(6, 'Mari', 1),
(7, 'Mordvinic', 1),
(8, 'Sami', 1),
(9, 'Baltic-Finnic', 1),
(10, 'Komi', 5),
(11, 'Komi-Permyak', 5),
(12, 'Udmurt', 5),
(13, 'Erzya', 7),
(14, 'Moksha', 7),
(15, 'Western Sami', 8),
(16, 'Eastern Sami', 8),
(17, 'Southern Sami', 15),
(18, 'Umi Sami', 15),
(19, 'Lule Sami', 15),
(20, 'Pite Sami', 15),
(22, 'Northern Sami', 15),
(23, 'Kemi Sami', 16),
(24, 'Inari Sami', 16),
(25, 'Akkala Sami', 16),
(26, 'Kildin Sami', 16),
(27, 'Skolt Sami', 16),
(28, 'Ter Sami', 16),
(29, 'Estonian', 9),
(30, 'Finnish', 9),
(31, 'Ingrian', 9),
(32, 'Karelian', 9),
(33, 'Livonian', 9),
(34, 'Veps', 9),
(35, 'Votic', 9),
(36, 'South Estonian', 29),
(37, 'Voro', 36),
(38, 'Karelian Proper', 32),
(39, 'Lude', 32),
(40, 'Olonets Karelian', 32);

这里有一个查询来演示:

mysql> SELECT t1.language AS lev1, t2.language as lev2, t3.language as lev3, t4.language as lev4, t5.language AS lev5
    -> FROM language_family_adj_list AS t1
    -> LEFT JOIN language_family_adj_list AS t2 ON t2.parent_id = t1.language_id
    -> LEFT JOIN language_family_adj_list AS t3 ON t3.parent_id = t2.language_id
    -> LEFT JOIN language_family_adj_list AS t4 ON t4.parent_id = t3.language_id
    -> LEFT JOIN language_family_adj_list AS t5 ON t5.parent_id = t4.language_id
    -> WHERE t1.parent_id IS NULL
    -> ORDER BY t1.language, t2.language, t3.language, t4.language, t5.language;
+-------------+---------------+--------------+------------------+------+
| lev1        | lev2          | lev3         | lev4             | lev5 |
+-------------+---------------+--------------+------------------+------+
| Finno-Ugric | Baltic-Finnic | Estonian     | South Estonian   | Voro | 
| Finno-Ugric | Baltic-Finnic | Finnish      | NULL             | NULL | 
| Finno-Ugric | Baltic-Finnic | Ingrian      | NULL             | NULL | 
| Finno-Ugric | Baltic-Finnic | Karelian     | Karelian Proper  | NULL | 
| Finno-Ugric | Baltic-Finnic | Karelian     | Lude             | NULL | 
| Finno-Ugric | Baltic-Finnic | Karelian     | Olonets Karelian | NULL | 
| Finno-Ugric | Baltic-Finnic | Livonian     | NULL             | NULL | 
| Finno-Ugric | Baltic-Finnic | Veps         | NULL             | NULL | 
| Finno-Ugric | Baltic-Finnic | Votic        | NULL             | NULL | 
| Finno-Ugric | Hungarian     | NULL         | NULL             | NULL | 
| Finno-Ugric | Khanty        | NULL         | NULL             | NULL | 
| Finno-Ugric | Mansi         | NULL         | NULL             | NULL | 
| Finno-Ugric | Mari          | NULL         | NULL             | NULL | 
| Finno-Ugric | Mordvinic     | Erzya        | NULL             | NULL | 
| Finno-Ugric | Mordvinic     | Moksha       | NULL             | NULL | 
| Finno-Ugric | Permic        | Komi         | NULL             | NULL | 
| Finno-Ugric | Permic        | Komi-Permyak | NULL             | NULL | 
| Finno-Ugric | Permic        | Udmurt       | NULL             | NULL | 
| Finno-Ugric | Sami          | Eastern Sami | Akkala Sami      | NULL | 
| Finno-Ugric | Sami          | Eastern Sami | Inari Sami       | NULL | 
| Finno-Ugric | Sami          | Eastern Sami | Kemi Sami        | NULL | 
| Finno-Ugric | Sami          | Eastern Sami | Kildin Sami      | NULL | 
| Finno-Ugric | Sami          | Eastern Sami | Skolt Sami       | NULL | 
| Finno-Ugric | Sami          | Eastern Sami | Ter Sami         | NULL | 
| Finno-Ugric | Sami          | Western Sami | Lule Sami        | NULL | 
| Finno-Ugric | Sami          | Western Sami | Northern Sami    | NULL | 
| Finno-Ugric | Sami          | Western Sami | Pite Sami        | NULL | 
| Finno-Ugric | Sami          | Western Sami | Southern Sami    | NULL | 
| Finno-Ugric | Sami          | Western Sami | Umi Sami         | NULL | 
+-------------+---------------+--------------+------------------+------+
29 rows in set (0.00 sec)

所以这是修改后的前序遍历树表模式:

CREATE TABLE language_family_mptt (
 language VARCHAR(30) NOT NULL,
 lft INT NOT NULL,
 rgt INT NOT NULL
) COLLATE utf8;

然后是迁移数据的递归存储过程:

TRUNCATE TABLE language_family_mptt;
SET max_sp_recursion_depth = 255;
DROP PROCEDURE IF EXISTS insert_branches;
DROP PROCEDURE IF EXISTS start_tree;
DELIMITER ~~

CREATE PROCEDURE start_tree()
BEGIN
    DECLARE language_field VARCHAR(100);
    DECLARE done INT DEFAULT 0;
    DECLARE insert_id INT;
    DECLARE source_id INT;

    DECLARE cursor1 CURSOR FOR SELECT language, language_id FROM language_family_adj_list WHERE parent_id IS NULL ORDER BY language;

    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;

    OPEN cursor1;
    read_loop: LOOP

        SET @my_left = 1;

        FETCH cursor1 INTO language_field, source_id;
        INSERT INTO language_family_mptt ( language, lft ) VALUES ( language_field, 1 );

        CALL insert_branches( source_id );

        UPDATE language_family_mptt SET rgt = @my_left + 1 WHERE lft = 1 AND rgt = 0;

        IF done THEN
            LEAVE read_loop;
        END IF;

    END LOOP;
    CLOSE cursor1;

END; ~~

CREATE PROCEDURE insert_branches( IN source_parent_id INT )
BEGIN
    DECLARE done INT DEFAULT 0;
    DECLARE next_source_parent_id INT DEFAULT NULL;
    DECLARE orig_left INT DEFAULT NULL;
    DECLARE language_field VARCHAR(100);    
    DECLARE cursor1 CURSOR FOR SELECT language_id, language FROM language_family_adj_list WHERE parent_id = source_parent_id ORDER BY language;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;

    OPEN cursor1;

    read_loop: LOOP

        FETCH cursor1 INTO next_source_parent_id, language_field;

        IF done THEN
            LEAVE read_loop;
        END IF;

        SET @my_left = @my_left + 1;

        INSERT INTO language_family_mptt ( language, lft ) VALUES ( language_field, @my_left ); 

        SET orig_left = @my_left;

        CALL insert_branches( next_source_parent_id );

        UPDATE language_family_mptt SET rgt = @my_left + 1 WHERE lft = orig_left AND rgt = 0 ;

        SET @my_left = @my_left + 1;

    END LOOP;
    CLOSE cursor1;
END; ~~

DELIMITER ;

结果如下:

mysql> SELECT CONCAT( REPEAT( ' ', (COUNT(parent.language) - 1) ), node.language) AS name FROM language_family_mptt AS node, language_family_mptt AS parent WHERE node.lft BETWEEN parent.lft AND parent.rgt GROUP BY node.language ORDER BY node.lft;
+---------------------------------+
| name                            |
+---------------------------------+
|    Finno-Ugric                  | 
|        Baltic-Finnic            | 
|            Estonian             | 
|                South Estonian   | 
|                    Voro         | 
|            Finnish              | 
|            Ingrian              | 
|            Karelian             | 
|                Karelian Proper  | 
|                Lude             | 
|                Olonets Karelian | 
|            Livonian             | 
|            Veps                 | 
|            Votic                | 
|        Hungarian                | 
|        Khanty                   | 
|        Mansi                    | 
|        Mari                     | 
|        Mordvinic                | 
|            Erzya                | 
|            Moksha               | 
|        Permic                   | 
|            Komi                 | 
|            Komi-Permyak         | 
|            Udmurt               | 
|        Sami                     | 
|            Eastern Sami         | 
|                Akkala Sami      | 
|                Inari Sami       | 
|                Kemi Sami        | 
|                Kildin Sami      | 
|                Skolt Sami       | 
|                Ter Sami         | 
|            Western Sami         | 
|                Lule Sami        | 
|                Northern Sami    | 
|                Pite Sami        | 
|                Southern Sami    | 
|                Umi Sami         | 
+---------------------------------+
39 rows in set (0.00 sec)

:D