I have several tables as below, which was created according

"""I have several tables as below, which was created according to a `third-party system`, application also runs under the database of this system(oracle).

Constraint failed in `Table `A, but it works in `Table B`, supposed I want to display e.name in `Table B` with code of `b.c.d.e.name`, the fronted page displayed exact data, and fronted page displayed `None` in `Table A` with code of `a.b.c.d.e.name`,
"""
    class A(models.Model):
        a_id = models.IntegerField(primary_key=True)
        b = models.OneToOneField('B', models.DO_NOTHING, related_name='+')

    class B(models.Model):
        b_id = models.IntegerField(primary_key=True)
        c = models.OneToOneField('C', models.DO_NOTHING, related_name='+')

    class C(models.Model):
        c_id = models.IntegerField(primary_key=True)
        d = models.OneToOneField('D', models.DO_NOTHING, related_name='+')

    class D(models.Model):
        d_id = models.IntegerField(primary_key=True)
        e = models.OneToOneField('E', models.DO_NOTHING, related_name='+')

    class E(models.Model):
        e_id = models.IntegerField(primary_key=True)
        name = models.CharField(max_length=64)


# Results of pdb as below:

    (Pdb) B.objects.using('third_party_db').get(c__d__e__name="Dog")
    *** general.models.B.MultipleObjectsReturned: get() returned more than one B -- it returned 1673!
    (Pdb) A.objects.using('third_party_db').get(b__c__d__e__name="Dog")
    *** general.models.A.DoesNotExist: A matching query does not exist.
    (Pdb) A.objects.using('third_party_db').get(b__c__pk=1)
    *** general.models.A.DoesNotExist: A matching query does not exist.
    (Pdb) A.objects.using('third_party_db').get(b__f__pk=1)
    *** general.models.A.MultipleObjectsReturned: get() returned more than one A -- it returned 18!