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Posted by Gnutt Halvordsson on 06/28/05 11:04
On Mon, 27 Jun 2005, Peter Albertsson wrote:
>
> "Gnutt Halvordsson" <gnutt@shell.linux.se> wrote in message
> news:Pine.LNX.4.63.0506272255520.8628@gnuttLap...
>> I'm trying to devel a grouping system for certain individuals.
>> The groupingsystem is meant to be built up like following
>>
>> Every group can have a finite number of child group, but only one parent.
>> So there will be a tree-structure to it all.
>> The grouping-system, I can work out. But the problem is, when viewing for
>> example the root, all individuals should be shown.
>>
>> If I go down one branch, I should be able to see everyone, who is part of
>> the group (which is the current branch) and all individuals placed on
>> branches further out from the root than this branch.
>>
>> So I should always be able to see those In the group, and people above it.
>>
>> I have no idea on how to do this, so any help is appriciated.
>>
>> //Gnutt
>
> On this page you have 2 different solutions to your problem plus links to a
> 3rd solution:
>
> http://www.sqlteam.com/item.asp?ItemID=8866
>
> Adjency lists is the simplest way, but only allows you to see a fixed number
> of steps up or down the tree by using self-joins. Very ugly and not dynamic.
> Recursion is usually used to traverse the tree.
>
> Nested sets is a little more complicated but allows you to do more advanced
> stuff with the tree (including to see all childs at all levels for a node),
> but it unfortunately has some performance problems. If you don't expect your
> tree to be very large, I think nested sets is the best solution for your
> problem.
>
> http://www.dbmsmag.com/9603d06.html
>
> http://www.dbmsmag.com/9604d06.html
>
> http://www.dbmsmag.com/9605d06.html
>
> http://www.dbmsmag.com/9606d06.html
>
> One can also use adjency lists with a "lineage" column, which I have never
> tried, but I don't THINK it will work very well for very deep trees.
>
> Nested sets and adjency lists can be combined to get around some of the
> performance problems with nested sets..
>
> This is a huge topic, so google on 'sql hierarchies' to learn more about
> it...
>
> Regards,
>
> Peter Albertsson
>
>
>
Thanks, this info gave me alot of ideas on how to solve other problems,
but unfortunatly not this one =P
These articles (as far as I can tell), lists all the parents to a specific
node, what I want, is to see all the childrens to it.
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