UNION to JPA Query

Question

Is it possible to query "UNION" in JPA and even "Criteria Builder"?

I'm looking for examples, but so far i got no result.

Does anyone have any examples of how to use it?

Or would that be with native sql?

Answer 1

SQL supports UNION, but JPA 2.0 JPQL does not. Most unions can be done in terms of joins, but some can not, and some are more difficult to express using joins.

EclipseLink supports UNION.

Answer 2

Depending on the case, one could use sub queries, something like:

select e from Entity e where e.id in (   select e.id   from Entity2 e2        join e2.entity e   where e2.someProperty = 'value' )       or e.id in (   select e.id   from Entity3 e3        join e3.entity e   where e3.someProperty = 'value2' )