How to delete parent child relation in Toplink

Question

Hi All,
I have 3 tables A,B,C.
In Table A ,I am saving record.
Table B & C has parent child relation.
B-->Parent
C-->Child
So I want to save records in Table A.
And delete from child(C) 1st then from parent(B).
I m writing my code as,
em.getTransaction().begin();
em.persist(Table A);//save in Table A
em.remove(em.merge(Table B));//Remove from Parent
But how to delete records from child table then from parent table.
Thanks
Sandip

Answer 1

If you have a @OneToOne relationship between two entities, the join column information is used to order the SQL when you remove two entities. For example, if I have:
@Entity
public class Employee implements Serializable {
     @OneToOne
     @JoinColumn(name="ADDR_ID")
     private Address address;
...Then the following code runs regardless of the order of the remove calls.
          em.getTransaction().begin();
          Employee parent = new Employee();
          Address child = new Address();
          parent.setAddress(child);
          em.persist(parent);
          em.persist(child);
          em.getTransaction().commit();
          em.getTransaction().begin();
          parent = em.merge(parent);
          child = em.merge(child);
          // order of next two statements unimportant
          em.remove(parent);
          em.remove(child);
          em.getTransaction().commit();If I don't remove the parent and just the child I get the same error you do because of the FK from Employee to Address.
--Shaun