Re: Trying to implent (Joe Celko's) Nested Sets, but need more data columns

From: Steve Kass (skass_at_drew.edu)
Date: 09/19/04 

Date: Sun, 19 Sep 2004 01:21:34 -0400

Joe Celko wrote:

>Do not keep the structure, which is a relationship, in the same table as
>the nodes, where is a set of entities.
>
>I have a new book out on nothing but trees & hierarchies in SQL that you
>might want to get. Nested sets are just one of many ways to model such
>things in SQL.
>
>But it looks like you need other help. The use of GUIDs is not
>relational; you are using PHYSICAL locators to get to your data and have
>no way of verifying them. You would be better off using IDMS or some
>other 1970's network database instead with kind of design.
>
>
If anyone using nonrelational features needs help, then don't you? The
lft and rgt columns of the nested set model are not relational, not
verifiable, and not stable.

It's possible to model hierarchies to obtain all the benefits of your
model and none of the failings, in a way that doesn't violate the theory
that Codd build: http://www.dbazine.com/tropashko4.shtml (followup
articles: http://www.dbazine.com/tropashko5.shtml and
http://www.dbazine.com/tropashko6.shtml).

Steve Kass
Drew University

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