RE: How-To select on a "group" function

Hi,

It's not possible to do this type of query using ODMG/OQL. 

You have to use the PB API. You can use the PB Style quries from
"within" ODMG - see
http://db.apache.org/ojb/docu/guides/odmg-guide.html#I+don%27t+like+OQL%
2C+can+I+use+the+PersistenceBroker+Queries+within+ODMG
for more details

Cheers,

Charles.

> -----Original Message-----
> From: Francesco Martinelli [mailto:[email protected]] 
> Sent: 22 November 2006 08:17
> To: Vasily Ivanov
> Cc: OJB Users List
> Subject: Re: How-To select on a "group" function
> 
> Thank you Vasily,
> however I am using ODMG, and I am not sure on how to 
> integrate your suggestion within ODMG.
> 
> Actually the sequence of instruction I use is the following:
>     Implementation odmg = OJB.getInstance();
>     Transaction tx = odmg.newTransaction();
>     tx.begin();
>     OQLQuery query = odmg.newOQLQuery();
>     String oqlQuery = "select ... from " + (Class)MyClass).getName();
>     query.create(oqlQuery);
>     Object queryResult = query.execute();
>     Iterator itr = ((ManageableCollection)queryResult).ojbIterator();
> 
> Thank you,
> Francesco.
> 
> 
> > Hi Francesco,
> >
> > You can do the following:
> > ReportQueryByCriteria query = 
> QueryFactory.newReportQuery(Clazz.class,
> > new Criteria());
> > query.setAttributes(new String[] { "max(value1)", "value2" }); 
> > query.addOrderByAscending("max(value1)");
> > query.addGroupBy("value2");
> > Iterator itr = pb.getReportQueryIteratorByQuery(query);
> >
> > I hope that helps.
> >
> > Regards,
> >   Vasily
> >
> > On 11/22/06, Francesco Martinelli <[email protected]> wrote:
> >> Hi,
> >>
> >> I would like to retrieve a record using the following SQL-Like
> >> statement:
> >> "select max(value) from " + className
> >>
> >> Does anyone know how to "convert" this to OQL?
> >>
> >> I know it would be possible to retrieve all the records, then sort 
> >> them out, and pick up the first, but I would prefer to reduce the 
> >> amount of data retrieved from the database.
> >>
> >> I also wonder if it were possible to order the "resultset" 
> according 
> >> to one field, e.g. of SQL-like would be:
> >> "select xxx from " + className + " order by value".
> >>
> >> Thenk you,
> >> Francesco.
> >>
> >>
> >> 
> ---------------------------------------------------------------------
> >> To unsubscribe, e-mail: [email protected]
> >> For additional commands, e-mail: [email protected]
> >>
> >>
> >
> 
> 
> 
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: [email protected]
> For additional commands, e-mail: [email protected]
> 
>