When there is a 1-to-many relationship defined in a JDG schema, the results from querying the "many" relationship may return the wrong results.

Example:

Person --> Phone Numbers
INSERT INTO Person(id,name,email) VALUES (1,'name1','email1')
INSERT INTO PhoneNumber(id, number) VALUES (1, '001234567');
INSERT INTO PhoneNumber(id, number) VALUES (1, '001234568');

SELECT p.name, p.id, pn.number FROM Person p, PhoneNumber pn WHERE p.id=pn.id AND p.id=1 and number = '001234568'
or
Select * from PhoneNumber where number = '001234568'

return 2 rows, 1 for each phonenumber.

Why? Because JDG returns the Person object that meets those conditions. It doesn't filter the internal data to the Person object. Therefore, all phonenumbers are returned for the same person, generating a row for each.

This doesn't happen with 1-to-1 relationships because there's only ever 1 child object.