Comments on: Storing hierarchical data in a database using ancestor tables

By: thomasrutter

thomasrutter — Sat, 07 Mar 2009 16:04:38 +0000

Ah yep, I see. I didn’t know there was a name for it either, and kinda assumed that since I couldn’t find anything else on it, maybe it has another name. If not, then I think ancestor tables is a good one

I’ve added extra columns to my implementation of it to allow me to sort the results in various orders, ie to do things like “find all descendants of node A and order them by creation date”, all using the one index. You could do this with a join and a sort afterwards.

By: vlad

vlad — Sat, 07 Mar 2009 13:40:33 +0000

Never knew there was a name for this method. I used it quite often.

My 2nd variant I use somethimes: nodeid, level, order

node level order
0 0 0
1 1 1
2 2 2
3 1 3

.. and i build quickly a tree like..

0
.. 1
.. .. 2
.. 3

Not as good as the ancestor table but in some cases is useful.

Glad to know i’m not the only one using ancestor tables.