Similar to bulk deletes, it is sometimes necessary to perform updates against a large number of queries in a single operation, without having to bring all the instances down to the client. Rather than bring these objects into memory and modifying them individually, JPA allows you to perform a single bulk update based on JPQL criteria.

Update by query uses the same JPQL syntax as normal queries, except that the query string begins with the update keyword instead of select. To execute the update, you call the following Query method:

public int executeUpdate ();

This method returns the number of objects updated. The following example updates all subscriptions whose expiration date has passed to have the "paid" field set to true..

Query q = em.createQuery ("update Subscription s set s.paid = :paid where s.subscriptionDate < :today");
q.setParameter ("today", new Date ());
q.setParameter ("paid", true);
int updated = q.executeUpdate ();