Re: Relationship between 2 models
Re: Relationship between 2 models
- Subject: Re: Relationship between 2 models
- From: email@hidden
- Date: Wed, 08 Oct 2003 10:44:51 CDT
- Priority: 3 (Normal)
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On Tue, 7 Oct 2003 12:22:24 -1000 Art Isbell wrote:
> On Tuesday, October 7, 2003, at 11:21 AM, Arturo Pirez wrote:
> You can't do anything in your eomodel that would generate SQL that
> joins tables in different DB's like flattening an attribute across a
> cross-eomodel relationship or flattening a cross-eomodel relationship.
> And you can't define a fetch spec in an eomodel or write one in code
> that involves attributes in different entities that model tables in
> different DB's or key paths that include a cross-eomodel relationship.
>
This is generally true, but sometimes there are ways around it. If you
have two models, but they really both point to the SAME database----that
is, they have IDENTICAL connection dictionaries---then EOF is supposed to
figure this out, and allow you to do anything you could do if it were one
model. I'm not sure how consistently this works.
Here's another experience: I use MS SQL Server 7. With that product, I
define multiple 'databases' all running on a single 'server instance'.
The db product does allow joings between these seperate 'databases', so
long as you use a fully qualified name of the tables involved. By
specifying the fully qualified names as the table external names in
EOModeler (things like 'dbName.dbo.tableName'), I've been succesful at
using SOME of the features that Art mentions, accross model-hopping
relationships. I think others of the features still don't work. And I'm
aware that if I ever change db products, or for that matter move some but
not other 'databases' to a new 'server instance', some of my code may
stop working.
--Jonathan
> It's unfortunate that one must be aware of these limitations, but I'm
> not sure that EOF could detect this and do the right thing
> automatically in all cases.
>
> Aloha,
> Art
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