Hierarchical Data Storage

[Trevor DeVore]

On Feb 12, 2007, at 12:54 PM, Bart Pietercil wrote:

> Hi Trevor,
>
> why wouldn't you organise it as Tree "lessons" ---> Node 1 Lesson  
> 1, Node 2 Lesson 1.1 Node 3 Lesson 2  and so one ?
>
> The Tree traversal method allows an unlimited number of Levels?
>
> Maybe I'm missing something (wouldn't be the first time)

Hi Bart,

In this particular db design lessons cannot have a parent lesson.   
Lessons are grouped into curriculums (which has a table of it's own  
as well).  So a lesson tree is just a single lesson and it's steps  
which is the combination of the lessons and steps table.

I think in either case you are left with the same problem though.  As  
I understand it, if you are going to have multiple people working on  
the database than how do you keep updates in on portion of the tree  
from affecting everything to the "right" of the current node?  It  
seems if you do change the left/right values for every record to the  
right of a node that any records other db editors might have open  
would be invalidated and have to be reloaded.


-- 
Trevor DeVore
Blue Mango Learning Systems - www.bluemangolearning.com
trevor at bluemangolearning.com