Question

I found this tutorial http://sqllessons.com/categories.html and I want to use the described method as it’s better than a recursive call but I have two problems:

1. How will I know the deepest level? In some page I may have 2 and in another I may have 20. Am I missing something or this method can be used only if you know the deepest level prior runtime!?

2. I have a multilingual database design, how can I change the queries to work with my table design below:

---

CREATE TABLE `categories` (
  `id` int(11) NOT NULL,
  `position` int(11) DEFAULT NULL,
  `parent_id` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `parent_id_fk` (`parent_id`),
  CONSTRAINT `categories_ibfk_1` FOREIGN KEY (`parent_id`) REFERENCES `categories` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `categories_locale` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `slug` varchar(100) NOT NULL DEFAULT '',
  `name` varchar(40) NOT NULL DEFAULT '',
  `category_id` int(11) NOT NULL,
  `locale_id` smallint(5) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Your help would be greatly appreciated.

Answer 1

You may want to consider researching ‘nested sets’. This article on nested sets is a good place to start. Also, if you are using an ORM (doctrine for example), nested set functionality is supported.