Re: Compound Primary Key foreign key references

Jakob Braeuchi Thu, 11 Mar 2004 12:05:00 -0800

hi wayne,

Wayne Kidd wrote:

Although this is, in fact the behavior of OJB, It seems that the right behavior should be to describe the referenced tables primary key in the sequence of the primary key definition. That is, if the primary key constraint gives the order as x,z,y then the referencing table should specify that its columns a,b,c refer to pk x,z,y with some syntax like <foreignkey field-ref="a" refers-to="x"/> <foreignkey field-ref="b" refers-to="z"/> <foreignkey field-ref="c" refers-to="y"/>


imo this would lead to less errors when using multicolumn-keys.
i opened a feature-request
http://nagoya.apache.org/scarab/issues/id/OJB249

jakob

instead of assuming the sequence of the column definitions in the other table.

Wayne

[EMAIL PROTECTED] wrote:
    My question was the later.  I could not find the behavior in the
documentation.
Thanks,

- Dan
-----Original Message-----
From: Ron Gallagher [mailto:[EMAIL PROTECTED]
Sent: Monday, August 18, 2003 9:53 AM
To: OJB Users List
Subject: Re: Compound Primary Key foreign key references
Dan --

Are you asking this question because you've tried this configuration and it doesn't work, or are you just confused as to how OJB will handle this situation? If the former, then please provide more info regarding the problems you're having. If the latter, then here's my explanation...

Anytime ojb encounters a reference-descriptor, it matches up the foreignkey elements, one for one, with the primary key field-descriptors in the referenced class. This matching process pairs up foreignkey and field-descriptor elements in the same order that they appear in the repository. So, in your case, the property mypackage.ClassA::keyA will be matched up with the property mypackage.ClassB::firstKey, and the property mypackage.ClassA::keyB will be matched up with the property mypackage.ClassB::secondKey
Ron Gallagher
Atlanta, GA
[EMAIL PROTECTED]
From: [EMAIL PROTECTED]
Date: 2003/08/18 Mon AM 09:01:37 EDT
To: [EMAIL PROTECTED]
Subject: Compound Primary Key foreign key references
All,
  From what I can tell, the repository.dtd is not sufficient to uniquely
reference an object with a compound primary key.  I think I must be
missing

something. In the contrived example below the foreign keys used to reference class B are keyA and keyB. Unfortunately, the names of keyA and keyB are NOT the same names inside classB. How do I configure refB to

tell
it that keyA references classB.secondKey and that keyB references
classB.firstKey or vica-versa.  I am a little unclear on how to make the
distinction explicit.  Any help will be appreciated.
- Dan
<class-descriptor  class="mypackage.ClassA"
 table="tableA"
 <field-descriptor
   name="id"
   column="id"
   jdbc-type="INTEGER"
   primarykey="true"
 />
 <field-descriptor
   name="keyA"
   column="keyA"
   jdbc-type="INTEGER"
 />
 <field-descriptor
   name="keyB"
   column="keyB"
   jdbc-type="INTEGER"
 />
 <reference-descriptor
    name="refB"
    class-ref="mypackage.ClassB"
 >
    <foreignkey field-ref="keyA"/>
    <foreignkey field-ref="keyB"/>
 </reference-descriptor>
</class-descriptor>
<class-descriptor  class="mypackage.ClassB"
 table="tableB"
 <field-descriptor
   name="firstKey"
   column="firstKey"
   jdbc-type="INTEGER"
   primarykey="true"
 />
 <field-descriptor
   name="secondKey"
   column="secondKey"
   jdbc-type="INTEGER"
   primarykey="true"
 />
</class-descriptor>
__________________________________________________ Daniel B. Brown | WELLS FARGO BANK MINNESOTA, N.A. | Software Architect | http://www.wellsfargo.com | MAC N2702-011 | 9062 Old Annapolis Road | Columbia | MD | 21045-1951 | p: 410.884.2034 | f: 410.715.2325 |
[EMAIL PROTECTED]
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Re: Compound Primary Key foreign key references

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