[jboss-user] [Persistence, JBoss/CMP, Hibernate, Database] - Join Fetch returning cartesian product

Apologies in advance if I'm asking something dumb here; I'm sure there's an obvious answer to this but I've just spent a day with my EJB3 book and on Google and haven't been able to find it. Imagine I have two entities - Parent and Child. Parent has a unidirectional one-to-many (lazy) relationship with Child, e.g:     @Entity     public class Parent {         @Id         private int id;         @OneToMany( cascade=CascadeType.ALL, fetch=FetchType.LAZY)         private List children = new ArrayList();         //snip     }     @Entity     public class Child {         @Id         private int id;         //snip     } [Note : my List and ArrayList in Parent are typed as containing Child objects but the syntax isn't being displayed here as it thinks it's XML.] Now imagine I have two Parents, each with three Child objects and I want a query to return all Parent objects including nested children: SELECT p FROM Parent p LEFT JOIN FETCH p.children I would expect this to return two Parent objects, but it returns six - each Parent object is repeated n times where n is the number of nested Child objects. If I use a "SELECT DISTINCT ..." then the problem is fixed, but that seems a strange thing to need to do and I'm wondering if it's necessary, or whether I'm missing something? Thanks in advance, Darren View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3965538#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...