Question

If I have two entity classes, Group and Person, where there is a one-to-many relationship between Group and Person (that is, a person can belong to at most one group, a group can have many persons), what jpql/hql query can I use to select all Persons not in Groups?

Something like the reverse of select p from Group g inner join g.people p…

Answer 1

This worked:

select p from Person p where p not in (select pg from Group g inner join g.persons pg)

Maybe:

select p from Person p where not exists (select 1 from Group g where p member of g.persons)

is more efficient?

In any case… comments are welcome as to which is more efficient, but since both of these “work”, marking the question as answered.