[eclipselink-users] Outer joined one-to-many question

[Laird Nelson <ljnelson@xxxxxxxxx>]

I have a parent entity with an optional one-to-many relationship with a child entity.

I am using LEFT OUTER JOIN in a query on the child entity.

The relevant excerpt from my query looks like this:

SELECT p.id

  FROM Parent i

  LEFT OUTER JOIN i.children child

If I want to end up returning a p.id object even when elements in that p.children relationship are not present--i.e. because the LEFT OUTER JOIN didn't find any related objects--how would I check for this?

I had something like this (this is the relevant fragment from the WHERE clause):

   AND (child IS NULL OR child.somethingOrAnother = 'someValue'...

When I do this, I get the following exception/warning in the logs:

Exception [EclipseLink-6076] (Eclipse Persistence Services - 2.3.2.v20111125-r10461): org.eclipse.persistence.exceptions.QueryException

Exception Description: Object comparisons can only be used with OneToOneMappings.  Other mapping comparisons must be done through query keys or direct attribute level comparisons. 

Mapping: [org.eclipse.persistence.mappings.OneToManyMapping[children]] 

To me, this looks like I can't really use "child" directly--as I am doing in that WHERE clause fragment.  Should I be doing something like:

   AND (IS EMPTY(child) OR child.somethingOrAnother = 'someValue'...

...instead?

Thanks,

Best,

Laird

--
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