Is JPA subquery in FROM clause possible?

Question

I\'m having a little problem with JPA. Consider this scenario:

Table A (id_a) | Table B (id_b, id_a)

What I need is a query

Answer 1

JPA does not support sub-selects in the FROM clause but EclipseLink 2.4 current milestones builds does have this support.

See, http://wiki.eclipse.org/EclipseLink/UserGuide/JPA/Basic_JPA_Development/Querying/JPQL#Sub-selects_in_FROM_clause

You can probably rewrite the query with just normal joins though.

Maybe,

Select a, size(a.bs) from A a

or

Select a, count(b) from A a join a.bs b group by a