Hi Theis,
As much as I can remember, there *is* - definitely - a need for an
intermediate third table to contain the mapping information. By using this
third table, you eliminate data replication/redundancy in the other two
tables.
To my knowledge this is a common technique. ER tools typically create such
an intermediate table for you when you select a relationship to be
'zero/one/many to many'. Whether you see that on your diagram is another
matter, but you will definitely see it in your DB ;)
Apologies if I have misunderstood your question.
Bye for now,
Tony.
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of
[EMAIL PROTECTED]
Sent: 22 January 2001 15:10
To: Orion-Interest
Subject: O/R mapping
Hi!
I have been reading the complex-or example and ploughed through the atm
example. In the complex-or example it is stated that collections are mapped
to an another table and that the reason for this is normalization. The Atm
example is also following this principle.
Is this really correct? I have never seen the necessity for mapping anone
to many relation to a third table (even though it was a long time ago I
read the rules of normalization I'm very doubtful that this is correct).
Could someone tell me the rational behind this.
If this not true, how does the xml look like (in the orion-ejb-jar.xml)
when you only map the relation as a foreign key?
Regards
/Theis
