How do I refer to columns only mapped for joins in JPQL?

Question

Let's say I have the following two tables:

@Entity public class Foo {
   @Id private int id;
   @ManyToOne()
   @JoinColumn(name = "bar_id")
   private Bar bar;
}
@Entity public class Bar {
   @Id private int id;
   private Boolean flag;
}

And I want to write a JPQL query that changes some Bar.flag values based on a collection of Foo ids.

If this were plain SQL I'd write something like this:

UPDATE Bar SET flag = true WHERE id IN (SELECT bar_id from FOO where id = 3);

You can't translate this to JPQL however, because the bar_id column isn't mapped to a property of the entity.

As bar_id isn't directly mapped on the Foo Entity, how can I achieve this kind of query in JPQL?

Answer 1

If you want a working bulk update query, the following should work:

UPDATE Bar b SET flag = true WHERE b IN (SELECT f.bar from FOO f where id = 3);

The idea is to work with entities, when you make the subselect.