Carlos Chávez wrote:
Dennis Riedel wrote:
Hello
I am new to OJB and asking myself, how to query multiple tables using
the persistenceBroker.
I cannot follow the example given on the OJB Query Page, I don`t
understand it.
I have three tables and all contain one column 'area_id'. I want to
find all entries in all tables containing a specific area_id, e.g. '2'.
So I think joining them would be the idea.
When I expect one resulting object of that query (there can be only
one result, that is a fact), of which type will this be?
I workd with DAO Classes to recieve a special object or a collection
of special objects.
But how is it, when I query on three tables, representing three
different objects? Do I need a wrapper? Should these three objects
implement the same interface to 'encapsulate' or 'wrap' the resulting
object?
With my actual knowledge I would query each table with its DAO but
that would be three queries to get the result.
I want one query.
Thanks for any support on querying multiple tables.
Hi Dennis.
you can use too ReportQueryByCriteria.
for example:
make criteria:
Crit criterio = new Criteria();
crit.addEqualTo("area_id", new Integer(2));
Create the Query:
ReportQueryByCriteria query = new ReportQueryByCriteria(Table1.class,
crit);
then you need to tell what fields you want in the result:
query.setAttributes(new String[] { "fieldName",
"pathToField.fieldName", "pathToField.fieldName"});
later you can obtain a collection of object[] where each item of the
array are each field, each item have a datatype equal to each field:
Iterator iter = broker.getReportQueryIteratorByQuery(query)
Then you can access to rows of the result.
Cheers.
Carlos Chávez.
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Thanks alot for your answer Carlos.
When I get you right, you query on one table (Table1.class in your
example). Is there any possibility to query on more than one table with
one query by the same criteria as posted above?
Regards,
Dennis
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