ODMG - MULTIPLE TABLES - Retrieval

[kishore talagadadeevi <kt...@hotmail.com>]

Hi,

I would like to know whether any known issues with ODMG api in handling 
multiple tables by mapping to  a single class. I need to just retrieve the 
data only . I have seen some documentation
explaining a mapping of a class to multile tables. But I want to know 
whether it is going to
work for my scenario or not before starting my coding ....

Requirement:
-----------------

I have three independent tables  .

All three tables have part_num and part_serial as part of composite primary 
key in addition to other columns.

Question: How do I retrieve  qty,cost and size by joining all three tables 
on part_num and
              part_serial columns using OJB ???

              How do I define this scenario as a class descriptor  in 
repository.xml file ???



TABLE_PARTA:
-------------------------

part_num(pk)
part_serial(pk)
system(pk)
qty


TABLE_PARTB
---------------------


part_num(pk)
part_serial(pk)
type(pk)
cost

TABLE_PARTC :
-----------------------
part_num(pk)
part_serial(pk)
dimension(pk)
size

Please throw some light on the above mentioned issue ...

Thanks in advance ...



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Re: ODMG - MULTIPLE TABLES - Retrieval

[Armin Waibel <ar...@apache.org>]

Hi,

kishore talagadadeevi wrote:

> Hi,
> 
> I would like to know whether any known issues with ODMG api in handling 
> multiple tables by mapping to  a single class.

Mapping a single class to multiple tables was currently not supported 
(insert does not work, reading should work but I never test this) by 
ODMG (PB-api support this feature).

> I need to just retrieve 
> the data only .

as said above, this could be work with odmg.

> I have seen some documentation
> explaining a mapping of a class to multile tables. But I want to know 
> whether it is going to
> work for my scenario or not before starting my coding ....
> 
> Requirement:
> -----------------
> 
> I have three independent tables  .
> 
> All three tables have part_num and part_serial as part of composite 
> primary key in addition to other columns.
> 
> Question: How do I retrieve  qty,cost and size by joining all three 
> tables on part_num and
>              part_serial columns using OJB ???
> 
>              How do I define this scenario as a class descriptor  in 
> repository.xml file ???
> 
> 

Don't know if I understand your question, but nevertheless I will try 
answer something ;-)

You can use 'Extents' with a base interface.
http://db.apache.org/ojb/docu/guides/advanced-technique.html#Extents

interface Part
{
get/setNum
get/setSerial
{

PartA,...C implement interface Part

In repository file declare class-descriptor for PartA,...C (with PK 
attribute for num + serial) and
define these classes as extents of Part

<class-descriptor class="Part">
    <extent-class class-ref="PartA" />
    <extent-class class-ref="PartB" />
    <extent-class class-ref="PartC" />
</class-descriptor>

Criteria crit = new Criteria();
[crit.addEqualTo("fieldName", value);]
crit.addEqualTo("partNum", 12);
crit.addEqualTo("serial", 123);
Query q = QueryFactory.newQuery(Part.class, crit);
Collection result = broker.getCollectionByQuery(q);

Will return all Part classes (PartA, ...C) with part_num 12 and 
part_serial 123


regards,
Armin

> 
> TABLE_PARTA:
> -------------------------
> 
> part_num(pk)
> part_serial(pk)
> system(pk)
> qty
> 
> 
> TABLE_PARTB
> ---------------------
> 
> 
> part_num(pk)
> part_serial(pk)
> type(pk)
> cost
> 
> TABLE_PARTC :
> -----------------------
> part_num(pk)
> part_serial(pk)
> dimension(pk)
> size
> 
> Please throw some light on the above mentioned issue ...
> 
> Thanks in advance ...
> 
> 
> 
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> To unsubscribe, e-mail: ojb-user-unsubscribe@db.apache.org
> For additional commands, e-mail: ojb-user-help@db.apache.org
> 
> 
> 

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