users@glassfish.java.net

Re: two questions for JPA

From: <glassfish_at_javadesktop.org>
Date: Fri, 13 Jun 2008 06:33:56 PDT

Hi,

yes, it is possible to select just the userid. You include the fields you want to return in the SELECT clause of the query:
  SELECT u.userid FROM User u WHERE ...

It is also possible to compare the two userid fields:
  SELECT ... FROM User u, User2 u2 WHERE u.userid = u2.userid

There is a better way in case the two User classes have a relationship. Suppose class User has a OneToOne relationship to class User2 (so it has a field called user2 of type User2). Then the following query could help:
  SELECT ... FROM User u JOIN u.user2 u2 WHERE ...

I hope that helps.

Regards Michael
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