Hello folks,

I have a optional one-to-one mapping

ClassA <-> ClassB

Now, I want all the instances of ClassA which do not have an associated instance of ClassB

How do I do that?

I have tried various options, but nothing seems to work.

thanks


SD

It is the exact opposite of

getSession().createCriteria(ClassA.class).createCriteria("classB").list();

Where classB is the name of the association (role) in this Association.

I am a bit stumped here!

I have one working solution.

I am using the following right now ->


Query query = getSession().createQuery("from ClassA as ca where not exists (from ClassB as cb where cb.classA=ca)");
query.list();

Is there a more efficient way to do the same?

Also, is there a way to do the same using Criteria API?

I have one working solution.

I am using the following right now ->


Query query = getSession().createQuery("from ClassA as ca where not exists (from ClassB as cb where cb.classA=ca)");
query.list();

Is there a more efficient way to do the same?

Also, is there a way to do the same using Criteria API?

Is your association bi-directional? If it is, you can check the nullness of the mappedBy instance in ClassA. Although that does end up generating sql much like you have (although I believe they end up comparing a count to 0), but it's shorter for you to write.

Hi kjordan2001,

Thanks for your reply.

I had tried that.

Unfortunately, it does not return any result.

Can you please guide me on how the query should like with an example.

Regards,


Shrivallabh

For HQL/JPQL: