Hi,

I have three Entity Beans: Client, Person and Cooperation of which the later may connect/reference the first two using a @OneToOne Relationship.

I'm looking for a EJB QL Query, which will return all the Person's, which are not referenced/contained in Cooperation's.

How would the Query look like?

All the following queries produced errors or did not return anything:

SELECT x.p FROM (SELECT p, cm FROM Cooperation AS cm LEFT JOIN cm.partner p) as x WHERE x.cm IS NULL

OR

FROM Partner p WHERE NOT EXISTS (SELECT cm FROM Cooperation cm WHERE cm.partner IS NOT NULL AND cm.partner=p)

public class Person implements java.io.Serializable
{
@Id @NotNull @Length(min=5, max=40)
String hostname;

String firstName;
String lastName;
String street;
...
}

public class Client extends Person implements java.io.Serializable
{
@OneToOne(cascade={CascadeType.ALL})
@PrimaryKeyJoinColumn
EmailAccount emailAccount;
...
}

public class Cooperation implements Serializable
{
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
long id;

@OneToOne(cascade={CascadeType.ALL})
Client client;

@OneToOne(cascade={CascadeType.ALL})
Partner partner;
...
}