HQL Question: (Simple) many-to-many Query

tkuchheuser · **Joined:** Wed Jan 16, 2008 5:35 am **Posts:** 1

Hello together,

i have this simple bidirectional many-to-many association with a join table:

Person.java

[..]
@ManyToMany(targetEntity = Area.class, cascade = {
CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REFRESH })
@JoinTable(name = "addr_person_to_area", joinColumns = { @JoinColumn(name = "person_nr") }, inverseJoinColumns = { @JoinColumn(name = "fachgebiet_nr") })
private List<Area> area;
[..]

Area.java

[...]
@ManyToMany(mappedBy = "area", targetEntity = Person.class)
private List<Person> person;
[...]

It works just fine.
But which HQL-Statement would I use if I wanted the following:

"return all AREA Objects that are NOT associated with a specific PERSON Object"

It seems I'm not getting this done right (tried it with joins/fetch etc).

Any help/ links appreciated.

Thank you very much in advance
Timo

gonzao_diaz · **Joined:** Mon Nov 26, 2007 2:29 pm **Posts:** 443

Provided you defined proper "equals" and "hashCode" methods in your Person and Area classes, you could get all the Areas that are related, then a list of all the Areas, and then subtract with removeAll (Java way, not Hibernate).

farzad · **Posted:** Wed Jan 16, 2008 2:06 pm

This might do it for you:

Code:

select ar from Area ar where ar.person is empty

Farzad-