Atrix,
If you think of a complex organization with several levels and many
departments. (Or a complex assembly with sub-assemblies.) Each
person is represented in a table by their ID number and two
integers. The interesting thing is that there is no reference to
superior or inferior employees... the only representation of their
status in the tree is the two integer values.
So you can get all subordinates, or, all superiors, with a single
multi table select using the between operator. Celko's example
also had a sample select that did some grouping, though I don't
recall it's mechanics.
The strongest argument for using something like this is that you
can delete a member and the hierarchy is easily preserved. I think
it was Ron Rose who posted the article reference initially... I think
his intent was to use it for BOM applications, which would be
equally elegant.
Ben Petersen
On 28 Oct 2002, at 11:04, Atrix Wolfe wrote:
> that sounds pretty interesting...
>
> if you wanted to get a node and all its children would you be able to
> do that in a single select statement without a loop for each level?
>
> ----- Original Message -----
> From: "Ben Petersen" <[EMAIL PROTECTED]>
> To: <[EMAIL PROTECTED]>
> Sent: Monday, October 28, 2002 12:22 AM
> Subject: Re: FK to PK on same table MkII
>
>
> > There was reference to a Joe Celko article where he discussed "a
> > modified reverse tree transversal algorithm" or something similar,
> > was also called something like "leaf and node".
> >
> > Parent and child relationships are tracked in one table. Each
> > member has two integer references which bound subordinate
> > member's integers. Relationships are added or changed by
> > increasing/ decreasing these integers for the effected member and
> > subordinates. It took an evening of messing around with the concept
> > to finally "get it", but it's pretty cool.
> >
> > Searching the archives for Celko will probably dredge it up. If not,
> > I have some light (very) code I think can find and pass on that
> > would provide an example (if i remember correctly).
> >
> > Ben Petersen
> >
> >
> >
> > On 27 Oct 2002, at 23:43, Bernie Corrigan wrote:
> >
> > > Hi Tom -
> > >
> > > This is the multi-level parts breakout problem. We
> > > discussed this
> > > on the list way back when and I can't locate the solution;
> > > however, there is one and you might already have it in your
> > > archive.
> > >
> > > Bernie
> > >
> > > ----------------------------------------
> > > At 09:09 AM 10/27/2002 +1100, you wrote:
> > > >G'day,
> > > >
> > > >I said:
> > > >~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > >I am wanting to create a parent child relationship
> > > >between trading entities in the same table so I can
> > > >allow users to report on just one trading entity or
> > > >all under multiple levels of holding companies.
> > > >
> > > >I have created the table TradingEntity and the PK
> > > >col is EntityID. I have just programmatically
> > > >added the col ParentEntityID to the table with a
> > > >FK on ParentEntityID to reference EntityID.
> > > >
> > > >When I try to make another structural change in the
> > > >object manager (delete SYS_ROWVER) I get the error
> > > >message [The referenced table TradingEntity does not
> > > >have a compatible Primary Key.]
> > > >
> > > >Which is the bug, allowing me to programmatically
> > > >create the FK or not allowing me to edit the table
> > > >after it is done?
> > > >
> > > >I know I can do it with a RULE, just interested to
> > > >know the "proper" way to do it in R:BASE.
> > > >~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > >But I was wrong.
> > > >
> > > >With this:
> > > >
> > > >CREATE TABLE `TradingEntity` +
> > > >(`EntityID` INTEGER NOT NULL +
> > > >('Value for EntityID cannot be null.') , +
> > > > `Org_ID` INTEGER NOT NULL +
> > > >('Value for Org_ID cannot be null.') , +
> > > > `HeaderReqs` TEXT (70) , +
> > > > `EntityName` TEXT (70) , +
> > > > `AddressID` INTEGER , +
> > > > `CNRowIDTel` INTEGER , +
> > > > `CNRowIDFax` INTEGER , +
> > > > `CNRowIDEmail` INTEGER , +
> > > > `CNRowIDURL` INTEGER , +
> > > > `EntityNote` TEXT (200) , +
> > > > `CrntAvailable` TEXT (1) DEFAULT 'Y' NOT NULL , +
> > > > `ParentEntityID` INTEGER , +
> > > > `SYS_ROWVER`= +
> > > > (IFNULL((SYS_ROWVER+1),0,(SYS_ROWVER+1))+
> > > >) INTEGER )
> > > >ALTER TABLE `TradingEntity` ADD PRIMARY KEY +
> > > >(`EntityID` ) +
> > > >('Values for rows in TradingEntity must be unique.',+
> > > > 'Cannot delete - values exist in another table.',+
> > > > 'Cannot update - values exist in another table.')
> > > >AUTONUM `EntityID` IN `TradingEntity` USING +
> > > >4. 1. NONUM
> > > >RULES 'Value must exist in TradingEntity ' +
> > > > FOR `TradingEntity` SUCCEEDS +
> > > > WHERE EXISTS (SELECT EntityID FROM TradingEntity
> > > > WHERE T+
> > > >radingEntity.EntityID = TradingEntity.ParentEntity+
> > > >ID )
> > > >
> > > >In the browser I cannot get the existing values
> > > >for EntityID accepted into ParentEntityID without
> > > >a rule violation message on exit from the last
> > > >row in the browser.
> > > >
> > > >Any clues?
> > > >
> > > >Warmest regards,
> > > >
> > > >
> > > >Tom Grimshaw
> > > >coy: Just For You Software
> > > >tel: 612 9552 3311
> > > >fax: 612 9566 2164
> > > >mobile: 0414 675 903
> > > >
> > > >post: PO Box 470 Glebe NSW 2037 Australia
> > > >street: 3/66 Wentworth Park Rd Glebe NSW 2037
> > > >
> > > >email: [EMAIL PROTECTED]
> > > >web: www.just4usoftware.com.au
> > > >
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