Re: Many To Many relationships across multiple databases [:|)
Re: Many To Many relationships across multiple databases [:|)
- Subject: Re: Many To Many relationships across multiple databases [:|)
- From: Brent Shank <email@hidden>
- Date: Thu, 27 Feb 2003 10:38:07 -0800
Here's a bit that from the EO book that may shed some light:
http://developer.apple.com/techpubs/webobjects/Enterprise_Objects/
Connecting/chapter_10_section_8.html
Brent
On Wednesday, February 26, 2003, at 11:39 AM, Jonathan Rochkind wrote:
At 09:04 AM 2/26/2003 -1000, Art Isbell wrote:
That's my experience as well even under WO 5.2. Flattened
relationships generate SQL join statements. When the tables involved
in the join are in different databases, many databases will generate
an error because they don't support joins across tables in different
databases.
Interestingly, in MS SQL Server you can do a cross-database join, as
long as the 'databases' are in the same SQL Server Instance. You just
need to put the 'dbo.' prefix in front of the table name in the
EOModel, and EOF ends up generating valid SQL code for cross-db joins
in MS SQL Server. I've used this trick to succesfully do other things
that would make EOF try a cross-db join with MS SQL Server.
(relationship-pre-fetching and qualifying-across-relationship-keypath
with relationships that span models/dbs comes to mind).
But cross-model/db flattened many-to-many STILL doesn't work, raising
mysterious EOF errors. So there's something else going on that makes
this not work, other than the cross-db join. What that is, I don't
know, I just know I learned not to bother trying.
--Jonathan
I've been able to create a many-to-many relationship across
eomodels by very carefully manually copying the configuration of a
many-to-many relationship created by EOModeler between 2 entities in
the same model. EOModeler won't create a many-to-many relationship
across different eomodels. But I've omitted the flattened
relationships and made the relationships underlying the flattened
relationships class properties when I will be traversing these
relationships in my app. Somewhat clunky, but it works.
Art
http://homepage.mac.com/aisbell/
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