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Re: [eclipselink-users] Outer joined one-to-many question 
On 8/19/2013 2:30 PM, Laird
Nelson wrote:

On Mon, Aug 19, 2013 at 2:22 PM, Andrei Ilitchev
<andrei.ilitchev@xxxxxxxxxx <mailto:andrei.ilitchev@xxxxxxxxxx>> wrote:

    How about:


    SELECT p.id <http://p.id>
       FROM Parent p
       LEFT OUTER JOIN p.children children
      WHERE
        children IS EMPTY OR
        EXISTS(SELECT child FROM Child child WHERE (child IN
    (p.children) AND child.x = 'y'))


Thank you.

This seems really complicated (the EXISTS and the subquery).  Could you
kindly tell me why the following is not supposed to work:
Even called "child" it still refers to a collection to be joined, not to a single collection member. 

SELECT p.id <http://p.id>
   FROM Parent p
   LEFT OUTER JOIN p.children child
  WHERE p.children IS EMPTY OR child.x = 'y'

...?  Does the query here return true in the non-empty case only when
all members of the collection have an x = ''y'?

As a side note, I noticed that none of the examples in the JPA
specification actually make use of the outer join they show.  The one
that shows up over and over is:

SELECT c FROM Customer c LEFT JOIN c.orders o WHERE c.status = 1

Note that neither c.orders nor o is referenced.

Thanks again for your time and help,
Best,
Laird

--
http://about.me/lairdnelson


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