MySQL 5.0 hierarchical recursive search - mysql

Question

I have a table like this
CREATE TABLE IF NOT EXISTS `categories` (
`id` INT(11) NOT NULL AUTO_INCREMENT,
`name` VARCHAR(150) NOT NULL,
`parent_id` INT(11) NULL,
`slug` VARCHAR(150) NOT NULL,
PRIMARY KEY (`id`),
)
This is an example of the table as how it is currently:
id name parent_id slug
----------------------------------------------------
1 Books NULL books
2 Anthology 1 anthology
3 Classic 1 classic
4 Drama 1 drama
5 Fable 1 fable
6 Aesop 5 aesop
7 Bidpai 5 bidpai
8 Stephen King 2 stephen-king
9 Magazines NULL magazines
10 Lifestyle 9 lifestyle
11 Wellness 9 wellness
12 Spa 11 spa
Note: i am on an old version of MySQL (5.0) so i cannot use recursive functions unfortunately
I want to select all parents and include them into the search result as well to get a nice overview of all the categories with the correct slugs in my application like this:
id name id_route slug
----------------------------------------------------
1 Books 1 books
2 Anthology 1,2 books/anthology
3 Classic 1,3 books/classic
4 Drama 1,4 books/drama
5 Fable 1,5 books/fable
6 Aesop 1,5,6 books/fable/aesop
7 Bidpai 1,5,7 books/fable/bidpai
8 Stephen King 1,2,8 books/anthology/stephen-king
9 Magazines 9 magazines
10 Lifestyle 9,10 magazines/lifestyle
11 Wellness 9,11 magazines/wellness
12 Spa 9,11,2 magazines/wellness/spa
Is it possible to retrieve a result like this in the first place? Because i am breaking my head around this at the moment. Any help or a push in the right direction would be amazing!

Answer 1

CREATE PROCEDURE GetTree()
BEGIN
CREATE TABLE tmp_cat LIKE categories;
ALTER TABLE tmp_cat ADD COLUMN path TEXT;
INSERT INTO tmp_cat (id, name, parent_id, slug, path)
SELECT id, name, parent_id, slug, name
FROM categories
WHERE parent_id IS NULL;
REPEAT
INSERT IGNORE INTO tmp_cat (id, name, parent_id, slug, path)
SELECT categories.id, categories.name, categories.parent_id, categories.slug, CONCAT(tmp_cat.path, ',', categories.name)
FROM categories
JOIN tmp_cat ON tmp_cat.id = categories.parent_id;
UNTIL ROW_COUNT() = 0
END REPEAT;
SELECT * FROM tmp_cat;
DROP TABLE tmp_cat;
END
fiddle

Answer 2

The following solution will work as far as you do NOT have more than three levels of hierarchy:
SELECT IF(level3_id IS NOT NULL, level3_id, IF(level2_id IS NOT NULL, level2_id, level1_id)) AS id,
IF(level3_name IS NOT NULL, level3_name, IF(level2_name IS NOT NULL, level2_name, level1_name)) AS name,
CONCAT_WS(",", level1_id, level2_id,level3_id) AS id_route,
CONCAT_WS("/", level1_slug, level2_slug,level3_slug) AS slug
FROM (
SELECT level1.id AS level1_id, level1.name AS level1_name, level1.slug AS level1_slug,
level2.id AS level2_id, level2.name AS level2_name, level2.slug AS level2_slug,
level3.id AS level3_id, level3.name AS level3_name, level3.slug AS level3_slug
FROM categories AS level1
RIGHT JOIN categories AS level2 ON level1.id = level2.parent_id
RIGHT JOIN categories AS level3 ON level2.id = level3.parent_id
) AS levels
ORDER BY id;
Sadly such solution will not scale up well. Recursive CTE is the better solution so you should consider upgrading.