I think I did not explain well.
The RDB DAS does not support containment (in the SDO sense) relationships
between business dataobjects in a graph. Since all elements must be
contained by something, all elements are contained by the (dummy) root of
the graph. So, if you read a department along with its related employees
then the relationship between department and employees is not containment.
Unless I misunderstand, this is what you want.
Here is one way to assign an existing employee to an existing department:
// Move an employee to dep1 from dep2
DataObject emp = (DataObject) dep2.getList("emps").get(0);
dep1.getList("emps").add(emp);
// Flush changes
das.applyChanges(root);
If the scenario you have in mind is more complicated than this - like if
you want to add employees that are not part of the existing graph - then
you are looking at merging graphs. There is some early support for this but
not much.
--Kevin
On 4/23/07, Umesh Tyagi (utyagi) <[EMAIL PROTECTED]> wrote:
But doesn't it pose a big limitation for DAS RDB ? I mean associations
are not necessarily containment relations. I want to able to assign an
existing employee to and existing department or a more intuitive example
would be relationship between "customer service agent" and "customer".
How am I ever going to achieve that with DAS RDB?
Thanks
-Umesh Tyagi
-----Original Message-----
From: Kevin Williams [mailto:[EMAIL PROTECTED]
Sent: Monday, April 23, 2007 3:07 PM
To: [email protected]
Subject: Re: RDB DAS - How to create non containment association ?
On 4/23/07, Umesh Tyagi (utyagi) <[EMAIL PROTECTED]> wrote:
>
> So whenever I want to associate employees to a department I either
> create a new employee or move employee from some other department ?
That's right.
I am talking about the case when a "employee" object is currently
> without any associated department. When we want to assign it to a
> department the following query will not include the employee I am
> interested in - "select * from DEPARTMENT left outer join EMPLOYEE on
> DEPARTMENT.ID = EMPLOYEE.DEPARTMENTID "
> A right join on the other hand will leave out all the 'departmemt'
> objects without any employee.
>
Thanks
> -Umesh Tyagi
>
>
> -----Original Message-----
> From: Kevin Williams [mailto:[EMAIL PROTECTED]
> Sent: Monday, April 23, 2007 12:43 PM
> To: [email protected]
> Subject: Re: RDB DAS - How to create non containment association ?
>
> If you want departments and their related employees then you would
> typically use a left join rather than a full join. At least, this is
> the scenario I see used most often. Our test case:
>
> RelationshipTests.testRelationshipModification2()
>
> demonstrates this.
>
> Thanks,
>
> --Kevin
>
>
>
> To read a set of departments and related employees you would typically
> use a left outer join rather than a full join since you want
>
> On 4/21/07, Umesh Tyagi (utyagi) <[EMAIL PROTECTED]> wrote:
> >
> > How to create non containment association between two existing
> > objects
> ?
> > For example, lets assume the following relationship is a non
> > containment association i.e. both objects can exist independently of
> > each other -
> >
> > ------------ ----------
> > |DEPARTMENT| 1______________* |EMPLOYEE|
> > ------------ ----------
> >
> > Playing with samples code I have noticed that in order to create
> > association between two object they need to be part of the same data
> > graph generated by a single query. So for the following line to work
> > -
> >
> > department.getList("employees").add(employee)
> >
> > both 'department' and 'employee' dataobjects must be under same root
> > DataObject instance. To achieve this I tried to do a full outer join
> > between DEPARTMENT and EMPLOYEE but it is not supported by derby or
> > hsql. The equivalent union result is not typed to DEPARTMENT and
> > EMPLOYEE by DAS. The other option is to set the foreign key value
> > explicitly in the 'employee' object, but it is not desirable. Any
> > other ideas ?
> >
> > -Umesh Tyagi
> >
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> >
> >
>
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