Hi Bryan,
I have few doubts. if u pls clearify them.
1.whats is flattened relationship?
2. cayenne has a tutorial with 3 tables Artist, gallery, painting. in datamap file there are db-relationship names like toGallery, toArtist,and paintingArray and with" targets", & "sorces". how did they relate them, did they give the relationship manullay without reenginering db schema or how?
In my case.
when i am reenginering db schema in cayenne modeler without the foreign key in the tables, i donot see any <db-relationship-name/pair>, if add the foreign keys and reenigering DB schema then i can see the db-relationship in the datamap.xml file.
what i have to do in my case.
sorry for bothering u.
Thanks
sami
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>>> brya..aine.rr.com 03/18/05 01:45PM >>>
I'm not a DBA type, but I've been down a similar learning curve.
Yes, it is possible to have relationships maintained only in the app. In
addition (optionally), the database can impose foreign-key constraints.
Using both approaches would give you a bit more protection against corrupted
data, in case there was a subtle bug in the application... if the app tried
to commit an invalid object graph, the database would catch it and cause an
exception to be thrown.
I believe it is fairly common practice to maintain relationships only in the
application, as your DBA is asking you to do. (In fact some databases might
not support foreign-key constraints.) It makes database maintenance tasks
somewhat easier. Especially when using Cayenne, which will do a good job of
validating the object graph before it's committed. Your application will
have an easier job of handling Cayenne's validation errors than
database-level exceptions, so this approach would probably be easier for you
as well.
If the application is successful (if it lives a long time and the database
grows large), you can always choose to go back later and add foreign-key
constraints to the database for that extra bit of protection, without
changing your application.
----- Original Message -----
From: "Sami Mohammed" <SMOHAMME..ndependenthealth.com>
To: <cayenne-use..bjectstyle.org>
Sent: Friday, March 18, 2005 11:28 AM
Subject: Foreign keys
My tables structure are given below:
1. User_table
user_key number primary key,
user_id varchar,
F&Lname varchar,
psswd varchar,
lastLogin date,
ActiveFlag char(1)
sec_master_key number referening to security_master_table(sec_master_key )
or foreign key
2.sec_master_Table Table:
sec_master_key number primarykey,
description varchar,
err_role_key number foreign key refering to table err_role_table,
cw_role key number foreign key refering to table cw_role_table,
last_chng_date date.
3.err_role_table
err_role_key number primary key,
err_role_id varchar,
err_role_description,
last_chng_date date
4. cw_role_table
cwr_role_key number primary key,
cw_role_id varchar,
errcw
last_chng_date date.
i have question:
in the above table structure if we remove the foreign keys and maintain the
relationship using in the application, is it possible. My db analyst ask me
to maintain in webappliction
i saw in ur tutorial and tutoriadb file in that also u dont have any
foreign key relationship for ARTIST, GALLERY and PAINTING tables.
But in the datamap.map file, i saw relationship. was it done manually or
what. I am using the techonolgy for quite some time, but still i am not
strong, may be i am asking some silly question. sorry for that.
see below for db-relationship
<db-relationship name="paintingArray" source="ARTIST" target="PAINTING"
toMany="true">
<db-attribute-pair source="ARTIST_ID" target="ARTIST_ID"/>
</db-relationship>
<db-relationship name="paintingArray" source="GALLERY" target="PAINTING"
toMany="true">
<db-attribute-pair source="GALLERY_ID" target="GALLERY_ID"/>
</db-relationship>
<db-relationship name="toArtist" source="PAINTING" target="ARTIST"
toMany="false">
<db-attribute-pair source="ARTIST_ID" target="ARTIST_ID"/>
</db-relationship>
<db-relationship name="toGallery" source="PAINTING" target="GALLERY"
toMany="false">
<db-attribute-pair source="GALLERY_ID" target="GALLERY_ID"/>
</db-relationship>
<obj-relationship name="paintingArray" source="Artist" target="Painting"
db-relationship-path="paintingArray"/>
<obj-relationship name="paintingArray" source="Gallery" target="Painting"
db-relationship-path="paintingArray"/>
<obj-relationship name="toArtist" source="Painting" target="Artist"
db-relationship-path="toArtist"/>
<obj-relationship name="toGallery" source="Painting" target="Gallery"
db-relationship-path="toGallery"/>
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any, are intended for the designated addressee only. If you are not the
designated addressee, you
are hereby notified that any disclosure, copying, or distribution of this
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