On Mon, 19 Aug 2002 23:47:23 -0500, Tom of Bunyon <[log in to unmask]>
wrote:

>I think the problem with MRP systems is that reational DBs don't do
>recursion very well - they have to emulate it. A lot of the more complex
>items have hugely complex sub-item trees. If the combination of trees
>exceeds the number of levels that the relational DBs program for, it just
>drops the deeper levels altogether with no complaints.

I have found the Oracle "connect by/start with" clause of the select
statement to be extremely usefull for creating a tree structure via one sql
command.


select  LEVEL, BOMNO, COMNO
from  PSF where ODATE > ? and EDATE <= ?
connect by prior COMNO = BOMNO
start with BOMNO = '1001';


This is quite handy for displaying/processing a tree structure.  Definitely
not the most effecient for MRP.  For MRP processing I would read in one
level at a time, as needed, and cache/recall these levels into/from main
memory.

Evan Vaala
Rockwell Automation

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