Re: Multiple Self-joins
Re: Multiple Self-joins
- Subject: Re: Multiple Self-joins
- From: David Holt <email@hidden>
- Date: Wed, 12 Jan 2005 12:12:28 -0800
Thanks Chuck,
I wasn't thinking clearly about the FKs. I was joining on
imageID>imageID in both cases. That make no sense whatsoever. So now I
have the to-one relationships cleared up. How do I implement the
to-many self join? I have made a to-one between parentFK>imagePK. Where
does the to-many relationship sit? Is there a link table?
I do not understand your suggestion for reordering the images. They are
process flows, so I could see having to reorder them in the future. In
fact it is guaranteed. Is there a resource that I could read to help me
understand what you are talking about?
On 12 Jan 2005, at 11:55 AM, Chuck Hill wrote:
On Jan 12, 2005, at 11:49 AM, David Holt wrote:
Hi Chuck,
I can create a to-one relationship (named parentImage) and a to-many
relationship (named childrenImages) linked on the primary key of the
image table.
Linked to what?
When I go to create an additional to-one relationship (nextImage or
previousImage),
Linking what to what?
the inspector in EOModeler shows the entities as already being
connected by their primary keys and the button is labelled
"disconnect". There is no way to create additional relationships
using the same primary keys without disconnecting the previous
relationship as far as I can tell.
Of course not. The same thing can't be different things at the same
time. Draw it out on a piece of paper. You need
pk
parentFK (PK value, but a FK in use) -> for parentImage, childImages
previousFK -> for previousImage
nextFK -> for nextImage
You might want to forget about the previousFK and nextFK and just use
an order column and make previous and next image methods on the
parent. It will be a lot easier to reorder like that.
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