Comments on: Storing hierarchical data in a database Part 2a: Modified preorder tree traversal

By: Manju

Manju — Mon, 01 Sep 2008 20:16:02 +0000

How to insert rows into this table? I mean how to calculate the left and right values? Please let us know.
Thanks,

By: Cameron Perry

Cameron Perry — Fri, 18 Jul 2008 05:03:24 +0000

Alan,

That third point is interesting and now doubt a fairly simple one to understand, however it seems to me somewhat impractical to use a method such as this when the total depth of the tree is unknown at any given point in the future. I think that is the downside of Chandler’s method – your tables could have an infinite number of columns, each of which are potentially filled with something. It is, however, easy on the eyes and simpler to understand than MPTT, though MPTT still reigns champ in my book.

By: Alan deLevie

Alan deLevie — Fri, 18 Jul 2008 00:51:09 +0000

@Phil:
I recently wrote about a (patented) method for storing hierarchical data in a database which does not require recursion for retrieving the tree as well as altering the tree. It is an improvement (in my opinion) over the path enumeration model.

Here’s the link: http://www.alandelevie.com/2008/07/12/recursion-less-storage-of-hierarchical-data-in-a-relational-database/

By: iamcam » Hierarchical data in a database2b: Modified preorder tree traversal - insertions

Sat, 15 Apr 2006 05:42:43 +0000

[...] Last time I introduced the Modified preorder tree traversal algorithm as a method to store relationships between nodes. This time I’ll show you how nodes are inserted into the tree. Note that I’m using MySQL, so you may need to change your queries slightly depending on the DB you’re using. [...]

By: iamcam

iamcam — Sat, 01 Apr 2006 10:00:49 +0000

I’m actually pretty new to the MPTT (blogging as I learn it), but I’ve already figured-out a lot beyond the Sitepoint article.

My next entry will dive a bit deeper where the Sitepoint article began getting shallow – namely in inserting nodes in specific places within the tree. I already pretty much figured-out conceptually how to move a node and its children, which is definitely another entry in and of itself. Here’s a hint: pull-out the node and its children from the DB into an array, delete those rows, do the appropriate math on the nodes to the right of the group, then at the insertion point, do some more math to make room for the node and children, INSERT into your DB the array you pulled out. Just make sure your math makes sense at each step and you should be fine.

I’ll get the next entry up as soon as I can…

By: Phil

Phil — Sat, 01 Apr 2006 00:02:49 +0000

I have been working with the Modified Preorder Tree Traversal and have been having difficulties writing an efficient method for moving a node with its child nodes.

I would be grateful if you could publish a method for doing this as my understading of the method is still not quite up to scratch.