JPA and aggregate functions. How do I use the result of the query?

Posted by Bogdan on Stack Overflow See other posts from Stack Overflow or by Bogdan
Published on 2010-05-26T09:16:23Z Indexed on 2010/05/26 9:21 UTC
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Hey guys,

I'm new to ORM stuff and I need some help understanding something.

Let's assume I have the following standard SQL query:

SELECT *, COUNT(test.testId) AS noTests FROM inspection
LEFT JOIN test ON inspection.inspId = test.inspId
GROUP BY inspection.inspId

which I want to use in JPA.

I have an Inspection entity with a one-to-many relationship to a Test entity. (an inspection has many tests) I tried writing this in JPQL:

 Query query = em.createQuery("SELECT insp, COUNT(???what???) FROM Inspection insp LEFT JOIN insp.testList " +
                              "GROUP BY insp.inspId");

1) How do I write the COUNT clause? I'd have to apply count to elements from the test table but testList is a collection, so I can't do smth like COUNT(insp.testList.testId)

2) Assuming 1 is resolved, what type of object will be returned. It will definitely not be an Inspection object... How do I use the result?

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