hi adid,
as carlos said, reportQueries are used to retrieve 'rows' not objects.
extending queryByCriteria to load only some attributes (fetch-groups in
jdo) is imo rather complicated. hibernate for example supports such lazy
attributes only by compiletime bytecode enhancement.
jakob
Abid Hussain schrieb:
Hi again,
first of all thanks for help.
Using distinct would lead to following SQL:
SELECT DISTINCT
A0.modul_Name,A0.Zuordnung,A0.Haeufigkeit,A1.MODUL_NAME,A1.BEREICH_NAME
FROM MODUL A0 INNER JOIN MODUL_BEREICH A1 ON A0.modul_Name=A1.MODUL_NAME
ORDER BY 1
I think this wouldn't solve the problem, because the wanted behaviour is
the following:
Retrieving data same as in QueryByCriteria, including the retrieval of
according collections, but retrieving only the fields/columns I actually
need.
It seems to be like Carlos said, one can't retrieve collections by using
the ReportQuery.
Isn't it a disadvantage that there is no possibility to restrict
QueryByCriteria in the way that only the wanted fields/collections are
retrieved?
In most cases, I don't need all columns of a table. And it causes a
great overhead, when I retrieve 30 columns but need only e.g. 3.
Don't get me wrong, I think OJB is a great tool, and it helps me a lot.
But wouldn't it be great having a method/class which combines the
simplicity of QueryByCriteria and the flexibility of ReportQuery?
Best regards,
Abid
Jakob Braeuchi schrieb:
hi abid,
what about using distinct ?
jakob
Abid Hussain schrieb:
Hallo again,
thanks for the quick answer.
When I add disciplines.moduleName and disciplines.disciplineName as
attributes for the ReportQuery it somehow works:
ReportQueryByCriteria q = QueryFactory.newReportQuery(Module.class,
crit);
q.addOrderByAscending("name");
q.setAttributes(new String[] {
"name", "courseOfStudy", "disciplines.moduleName",
"disciplines.disciplineName" });
OJB generates following SQL:
SELECT
A0.modul_Name,A0.Zuordnung,A0.Haeufigkeit,A1.MODUL_NAME,A1.BEREICH_NAME
FROM MODUL A0 INNER JOIN MODUL_BEREICH A1 ON
A0.modul_Name=A1.MODUL_NAME ORDER BY 1
But there is one major disadvantage about it: The retrieved Modules
occure as often in the resulting collection as they are referenced in
the ModuleDiscipline. E.g., when a Module has three according rows in
the table ModuleDiscipline, it occurs three times in the result of
the query above.
Maybe there is another way to fix this problem?
Best regards,
Abid Hussain
Carlos Chávez schrieb:
Abid Hussain escribió:
Hallo everybody,
for the following problem I didn't find a proper solution:
I'm using the ReportQuery to retrieve data, because the table has
about 25 columns and i only need a few. The problem is, in the
ReportQuery I can only specifiy the fields which I want to
retrieve, but no collections.
I've got the following classes/tables:
<class-descriptor class="modulverwaltung.beans.ojb.Module"
table="MODUL">
<field-descriptor name="name" column="modul_Name"
jdbc-type="VARCHAR" primarykey="true" />
<field-descriptor name="courseOfStudy" column="Zuordnung"
jdbc-type="VARCHAR" />
...
...
<collection-descriptor name="disciplines"
element-class-ref="modulverwaltung.beans.ojb.ModuleDiscipline"
orderby="disciplineName" sort="ASC">
<inverse-foreignkey field-ref="moduleName" />
</collection-descriptor>
</class-descriptor>
<class-descriptor class="modulverwaltung.beans.ojb.ModuleDiscipline"
table="MODUL_BEREICH">
<field-descriptor name="moduleName" column="MODUL_NAME"
jdbc-type="VARCHAR" primarykey="true" />
<field-descriptor name="disciplineName" column="BEREICH_NAME"
jdbc-type="VARCHAR" primarykey="true" />
</class-descriptor>
To retrieve date from the table MODUL, I could do like this:
QueryByCriteria q = new QueryByCriteria(Module.class,
QueryByCriteria.CRITERIA_SELECT_ALL);
q.addOrderByAscending("name");
c = broker.getCollectionByQuery(q);
But then all the fields from the according table would be
retrieved, whereas I only need two fields plus the specified
collection.
On the other hand, when I use a ReportQuery in order to retrieve
only the fields I actually need, I can't specify the collection in
the ReportQuery.
Did you try disciplines.moduleName and disciplines.disciplineName
as attributes for the ReportQuery ?
Cheers,
Carlos Chávez.
Anybody got an idea what I can do?
Best regards,
Abid Hussain
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