RE: [PHP] Category and sub-category logic
| From: | Chris W. Parker | Date: | Fri, 15 Aug 2003 00:04:00 +0000 |
| Subject: | RE: [PHP] Category and sub-category logic | ||
| Groups: | php.general | ||
| Request: | Send a blank email to php-general+get-159621@lists.php.net to get a copy of this message | ||
David Otton <mailto:phpmail@jawbone.freeserve.co.uk>
on Thursday, August 14, 2003 4:58 PM said:
> The advantage of doing it this way is that your tree structure is
> generic and can have many levels. The disadvantage is that you may
> need many SQL queries to fully traverse the tree (though people
> rarely want to do this, and sub-selects, clever joins or post-query
> processing can reduce the overhead).
Which is why you should use the Modified Preorder Tree Traversal method
instead. With that method you've got one table that defines the
categories AND their relationships to each other.
Your SQL queries end up looking something like this.
SELECT name
FROM categories
WHERE lft >= x
AND rgt <= y
Chris.