Hi,

I need help on hibernate mapping, am too confused on this, plz suggest me the approach.

i have table and A, B and C

A is parent table, and B, C are child objects.

There is id coloumn in primary key of table A refered to foreign key to the B and C,

suppose if am searching based on some field, it should retrive the vale from the table B and C. mostly all columns will be same in both table B and C.

query like

select * from B where type="q" union select * from C where type="q"

i have confused on using join-subclass or some other, could you plz tell me wat are the ways we can do this.

If ClassA has properties for ClassB and ClassC, you may use a many-to-one (if single instance):
<many-to-one name="itemB" column="ID" class="ClassB"/>
<many-to-one name="itemC" column="ID" class="ClassC"/>

or for collection
<class name="ClassA" table="TABLEA">
...
<set name="itemB">
<key column="ID"/>
<one-to-many class="ClassB"/>
</set>
<set name="itemC">
<key column="ID"/>
<one-to-many class="ClassC"/>
</set>
</class>


If you want a union, you may write a loader query:
<class name="ClassA" table="TABLEA">
<id name="id" column="ID">
<loader query-ref="loadClassBC"/>
...
</class>

<sql-query name="loadClassBC">
<return alias="bc" class="ClassBC"/>
select b.ID as {bc.id},
...
from TABLEB b
where b.ID = ?
union
select c.ID as {bc.id},
...
from TABLEB c
where c.ID = ?
</sql-query>


---
please rate

Thanks a lot lin, i have one more doubt,

<set name="itemB">
<key column="ID"/>
<one-to-many class="ClassB"/>
</set>
<set name="itemC">
<key column="ID"/>
<one-to-many class="ClassC"/>
</set>
</class>

in that <one-to-many class="ClassB"/> defines one record in class A, but B have many records rite?

and i am searching colum with present in table b and its not in table A, will it give the search results or we can able to search only column present in the table A?

plz correct me,if am wrong.

Here we are mapping ClassA. ClassA contains a set of ClassB called itemB (may be we should call it itemBs as it is a collection). You would need to map ClassB also.
Now, if you load ClassA, it would select data from ClassB and populate the set itemBs. Is this what you are trying to achieve?

---
please rate

Hi Lin,

Acutally my requirment is,

i need to search from the table b and table c, table a is parent, but its contain only few columns of the child table b anc table c.

so if am search based on columns like name, it should retrieve the records from b and c its like union.

this is my requirment, so how can we create serialise object, so the parent contain all the child columns fields?

There's no union in HQL but you could do something like

hi

this is another way to approach with collections

here is a complete sample on how to join tables. You can download and explore the source code.
http://forum.hibernate.org/viewtopic.php?t=994020&highlight=hibernate+sample

Thanks lin and msantos. i will try with these options..