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JPA query with hierarchy [message #666422]

Wed, 20 April 2011 12:23

moloco

Messages: 7
Registered: March 2010

Junior Member

Sorry for my bad EN Embarrassed

I have class hierarchy (JOINED) for example

class A { field a }

class B extends A { field b }
class C extends A { field c }

how can i get all objects filtered by fields a,b,c

in SQL it very simple

select * from A
left join B on ...
left join C on ...
where A.a = ... or B.b = .... or C.c = .....

how in JPQL ??

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Re: JPA query with hierarchy [message #666670 is a reply to message #666422]

Thu, 21 April 2011 14:01

James Sutherland

Messages: 1939
Registered: July 2009
Location: Ottawa, Canada

Senior Member

EclipseLink has a TREAT keyword that allows casting to a subclass, but it is more for accessing a relationship, not the root class,

i.e.

Select e from Employee e join TREAT(e.projects AS LargeProject) lp where lp.budget = value

I think you would need to execute multiple queries in JPQL, one for each subclass you want to query something on.

Otherwise you can use a native SQL query.

I think the issue is similar to,

https://bugs.eclipse.org/bugs/show_bug.cgi?id=312146

So you may wish to add your requirements to that bug and vote for it.

James : Wiki : Book : Blog : Twitter

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