Question

select x from X x where x.a.id = :a_id –> Always 0 objects selected

Why does the above JPQL statement not work, but the one below work?

select a from A a where a.id = :a_id –> a_obj
select x from X x where x.a = :a_obj –> Always correct number of objects selected

Neither query throws an exception during execution, but a different number of results are obtained.

Thanks

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Update

I tried the following queries by using joins:
select x from X x, x.a a where x.a.id = :a_id –> TopLink exception for unexpected token

and this:
select x from X x JOIN x.a a where a.id = :a_id –> Always correct number of objects selected

With the latter query, I have solved the initial problem at hand. However, now I have got two queries which should work, but for some reason don’t.

select x from X x where x.a.id = :a_id –> Always 0 objects selected
select x from X x, x.a a where x.a.id = :a_id –> TopLink exception for unexpected token

Has anyone else encountered similar behaviour?

Answer 1

I think you have to also bring in entity a in the first example so that it’s attributes are visible.

Something like

select x from X x join fetch x.a where x.a.id = :a_id

(I don’t use JPA, I stick to HQL, so this is untested, unproven and comes without a money-back guarantee.)