Algorithm SQL中邻接表到前序树遍历的递归查询?
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。旧的 schema有一个基于邻接列表的分类系统,具有 id、category和parent_id。如果一个category在另一个之下,则 类别将第二个id作为其父id。例如:Algorithm SQL中邻接表到前序树遍历的递归查询?,algorithm,data-structures,rdbms,nested-sets,rdbms-agnostic,Algorithm,Data Structures,Rdbms,Nested Sets,Rdbms Agnostic,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。旧的 schema有一个基于邻接列表的分类系统,具有 id、category和parent_id。如果一个category在另一个之下,则 类别将第二个id作为其父id。例如: +-------------+----------------------+--------+ | category_id | name | parent | +-------------+----------------------+-
+-------------+----------------------+--------+
| 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 |
+-------------+----------------------+--------+
新模式有一个修改的前序树遍历算法:
+-------------+----------------------+-----+-----+
| 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 |
+-------------+----------------------+-----+-----+
文章中的例子
无论如何,我有能力或编写一个带有递归函数的php脚本
这将把邻接列表迁移到预排序树结构。
基本上,对于每一行,它都会插入一个空白的“rgt”值,看起来
对于儿童,将函数递归地应用于他们,保持跟踪
,然后更新“rgt”值
但我想在纯SQL中实现这一点。然而,我知道的还不够多
它的立足点。首先,我不知道你是否可以用
递归查询,或者如果有其他方法来实现它 这是我得到的;这是一个例子,可以根据您的情况进行概括或调整 首先,我将建立一个邻接列表(来自维基百科的语系数据): 下面是一个要演示的查询:
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)
下面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;
下面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您是否有已知数量的层次结构级别-这是一个静态数据集,还是需要处理“任何”数据集?在我处理的数据集中,它或多或少是静态的,因此存在已知级别。但我确实在寻找一个通用算法。递归存储过程…非常好。我尝试过这个,但“rgt”列未填充,lft值正常,但所有行的rgt都为空。我只是在mysql 5.1.63-0+debian上通过复制/粘贴尝试了这一点,并且工作正常。原始邻接列表是否正确填充?
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)