include only some of the top stack entries and only relevant descriptors
from your repository.
jakob
----- Original Message -----
From: "Rudi Alberda" <[EMAIL PROTECTED]>
To: "OJB Users List" <[EMAIL PROTECTED]>
Sent: Friday, October 04, 2002 12:02 PM
Subject: Re: Query on collections
> I'll post the sample later on when I have some more time.
> Do you want the entire stack trace along with the repository and the code
> that generates it? Because it's an awful lot (we've got a big repository
> with loads of objects)
>
> ----- Original Message -----
> From: "Jakob Braeuchi" <[EMAIL PROTECTED]>
> To: "OJB Users List" <[EMAIL PROTECTED]>
> Sent: Friday, October 04, 2002 10:51 AM
> Subject: Re: Query on collections
>
>
> > hi rudi,
> >
> > > Oh my... so that actually works! Wow... I tried it and it
> > > seemed OJB generates the SQL that we did before 'by hand',
> > > so that's perfect! Just wish I'd known about this sooner,
> >
> > well, we invested a lot of time to keep users happy...
> >
> > > 'The correlation name 'A3' is specified multiple times in a FROM
> clause.'
> > > which was indeed the case. Is this a bug?
> >
> > can you please post the sample and the generated sql ?
> >
> > jakob
> >
> > ----- Original Message -----
> > From: "Rudi Alberda" <[EMAIL PROTECTED]>
> > To: "OJB Users List" <[EMAIL PROTECTED]>
> > Sent: Friday, October 04, 2002 9:30 AM
> > Subject: Re: Query on collections
> >
> >
> > > Oh my... so that actually works! Wow... I tried it and it
> > > seemed OJB generates the SQL that we did before 'by hand',
> > > so that's perfect! Just wish I'd known about this sooner,
> > > there is no mentioning of this in any tutorial.
> > > One more thing; when I tried to add 2 criteria on an m:n
> > > relation (on a m:n relation and its parent), the generated
> > > SQL was not accepted by SQL server 2000 and I got an exception
> > > saying something about
> > > 'The correlation name 'A3' is specified multiple times in a FROM
> clause.'
> > > which was indeed the case. Is this a bug?
> > >
> > > ----- Original Message -----
> > > From: "Jakob Braeuchi" <[EMAIL PROTECTED]>
> > > To: "OJB Users List" <[EMAIL PROTECTED]>
> > > Sent: Thursday, October 03, 2002 5:36 PM
> > > Subject: Re: Query on collections
> > >
> > >
> > > > hi rudi,
> > > >
> > > > this snippet is from test case QueryTest:
> > > >
> > > > Criteria crit = new Criteria();
> > > > crit.addEqualTo("projects.title", "HSQLDB"); // direct m:n
> > > > Query q = QueryFactory.newQuery(Person.class, crit);
> > > > Collection results = broker.getCollectionByQuery(q);
> > > >
> > > > it's looking for persons working on project named "HSQLDB"
> > > >
> > > > hth
> > > > jakob
> > > >
> > > > ----- Original Message -----
> > > > From: "Rudi Alberda" <[EMAIL PROTECTED]>
> > > > To: "OJB Users List" <[EMAIL PROTECTED]>
> > > > Sent: Thursday, October 03, 2002 2:44 PM
> > > > Subject: Re: Query on collections
> > > >
> > > >
> > > > > Hey Chris,
> > > > >
> > > > > Thanks for your tip, but we (and indeed I forgot to mention this)
> > > already
> > > > do
> > > > > the query on m:n
> > > > > objects like this (except we use 'hard' table names and PK field
> > names).
> > > > > What I was wondering
> > > > > was if there was an easier way to do it than like this :)
> > > > >
> > > > > For example something like this would be extremely cool to have in
> > OJB:
> > > > > Criteria c = new Criteria();
> > > > > c.addIn("bees[]", B);
> > > > > Query q = new QueryByCriteria(B.class, c, false);
> > > > > broker.getCollectionByQuery(q);
> > > > >
> > > > > or even
> > > > > Criteria c = new Criteria();
> > > > > c.addEqualTo("bees[0].name", B.getName());
> > > > > Query q = new QueryByCriteria(B.class, c, false);
> > > > > broker.getCollectionByQuery(q);
> > > > >
> > > > > Nevertheless, thanks for your input! :)
> > > > >
> > > > >
> > > > > ----- Original Message -----
> > > > > From: "Chris Lewington" <[EMAIL PROTECTED]>
> > > > > To: "OJB Users List" <[EMAIL PROTECTED]>
> > > > > Sent: Thursday, October 03, 2002 2:28 PM
> > > > > Subject: Re: Query on collections
> > > > >
> > > > >
> > > > > > Hi Rudi,
> > > > > >
> > > > > > I had to address a similar problem as part of implementing a
> "query
> > by
> > > > > object"
> > > > > > mechanism (tricky!) to search on "partially complete" objects
> rather
> > > > than
> > > > > using
> > > > > > straight queries themselves.. The basic idea I had was as
follows:
> > > > > >
> > > > > > - build an empty A and set your concrete B into its collection
> (use
> > > this
> > > > > as a
> > > > > > basis for what follows);
> > > > > >
> > > > > > - use the CollectionDescriptor of class A to get the FK column
> names
> > > of
> > > > > the
> > > > > > indirection table to both the item class (B) and the "this"
class
> > (A),
> > > > and
> > > > > also
> > > > > > the name of the indirection table itself;
> > > > > >
> > > > > > - then, from your concrete B, use its ClassDescriptor to get the
> PK
> > > > field
> > > > > info
> > > > > > and hence from that a PersistentField from which you can obtain
> the
> > > > actual
> > > > > PK
> > > > > > value of your B object;
> > > > > >
> > > > > > - then build a Criteria object with the following:
> > > > > > 1) an "addEqualToColumn" which matches the PK field for A to
its
> > > > > > corresponding column name in the indirection table, plus
> > > > > > 2) an "addEqualTo" which matches the actual PK value you have
for
> B
> > > > with
> > > > > its
> > > > > > corresponding column name in the indirection table;
> > > > > >
> > > > > > - then finally create a "QueryByMtoNCriteria" with the class of
A,
> > the
> > > > > > indirection table name and the newly built Criteria object.
> > > > > >
> > > > > > From there you can do a getCollectionByQuery with your newly
built
> > > Query
> > > > > object
> > > > > > above. I'm sure there are easier ways but that was the easiest I
> > could
> > > > > come up
> > > > > > with for now and it works OK for me.
> > > > > >
> > > > > > Hope that helps,
> > > > > >
> > > > > > Cheers,
> > > > > >
> > > > > >
> > > > > > Chris
> > > > > >
> > > > > > Rudi Alberda wrote:
> > > > > >
> > > > > > > Hi all,
> > > > > > >
> > > > > > > I have a question regarding queries on m:n relations. Suppose
I
> > have
> > > > two
> > > > > > > classes which are associated in OJB through a m:n relation,
> > objects
> > > of
> > > > > type
> > > > > > > 'A' and 'B'. 'A' has a property called 'bees' returning all
> > objects
> > > of
> > > > > type
> > > > > > > 'B', 'B' has a property called 'as' which returns all 'A'
> objects.
> > > > > > > This all works nicely in OJB, storing, updating, deleting. But
> now
> > I
> > > > > want to
> > > > > > > query. I have an object of type 'B' and I want to know which
> > objects
> > > > of
> > > > > type
> > > > > > > 'A' are associated to it. In other words, I'd like a query
which
> > > > results
> > > > > in
> > > > > > > a collection of 'A' objects for which 'B' is in the collection
> > > > 'A.bees'.
> > > > > > > How would this work?
> > > > > > > I cannot simply go and create a query like:
> > > > > > >
> > > > > > > Criteria c = new Criteria();
> > > > > > > c.addEqualTo("bees", B);
> > > > > > > Query q = new QueryByCriteria(B.class, c, false);
> > > > > > > broker.getCollectionByQuery(q);
> > > > > > >
> > > > > > > because bees is a collection. Will Criteria.addIn work? And if
> > this
> > > > > doesn't,
> > > > > > > what will?
> > > > > > > I have looked at QueryByMtoNCriteria but the documentation of
> this
> > > was
> > > > > > > rather unclear.
> > > > > > > Also, I might be able to use Criteria.addExists, but I need to
> > refer
> > > > to
> > > > > a
> > > > > > > field from the main query in the subquery, otherwise my
subQuery
> > > isn't
> > > > > of
> > > > > > > much use.
> > > > > > > Help!
> > > > > > >
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