我正在将数据从一个数据库模式迁移到另一个数据库模式。老人 schema具有基于邻接列表的分类系统 id，category和parent_id。如果一个类别低于一秒，那就是 category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 |
+-------------+----------------------+--------+
新架构具有修改的预订树遍历算法：
+-------------+----------------------+-----+-----+
| 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 |
+-------------+----------------------+-----+-----+
从文章Managing Hierarchical Data in MySQL中获取的示例。
无论如何，我有能力或写一个带有递归函数的php脚本 这会将邻接列表迁移到预订树结构。 基本上对于每一行，它都插入一个空白的'rgt'值，看起来 对于儿童，递归地应用函数，跟踪它们 计数器，然后更新'rgt'值。
但我想在纯SQL中这样做。但是，我不知道得到什么 立足于此。首先，我不知道你是否可以这样做 递归查询，或者是否有其他方法可以执行此操作。
答案 0 :(得分：6)
这就是我所得到的;这是一个例子，可以推广或适应您的情况。
首先，我将建立一个邻接列表（来自维基百科的语言族数据）：
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);
这是一个用于演示的查询：
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;
接下来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