Hibernate Criteria Subquery

Question

I need to do this SQL query with detachedCriteria:

SELECT g.id FROM games g
WHERE NOT EXISTS (
    SELECT 1 FROM users_games ug WHERE ug.user_id = 1 AND g.id = ug.game_id)

The idea is to get the ids from the games that aren't owned by the user. I tried like 10 different approaches with detachedCriteria but I get the "Unknown entity: null" MappingException The code should look like:

DetachedCriteria subquery = DetachedCriteria.forClass(UserGame.class, "ug")
   .add(Restrictions.eq("ug.user.id", 1))
   .add(Restrictions.eqProperty("ug.game.id","u.id"));
DetachedCriteria criteria = DetachedCriteria.forClass(Game.class, "g")
   .add(Subqueries.notExists(subquery));

Setting also the projections to return only the id of the games.

Any ideas? I think Hibernate has some trouble joining the queries with no alias. Adding alias works but the results are quite wrong.

Answer 1

You need to add an alias, as follows:

DetachedCriteria subquery = DetachedCriteria.forClass(UserGame.class, "ug")
   .addAlias("ug.user", "user")
   .add(Restrictions.eq("user.id", 1))
   .addAlias("ug.game", "game")
   .add(Restrictions.eqProperty("game.id","u.id"));

That should help