Question

I’m trying to write a fairly complex JPQL statement that sorts results based on a value in another table. I know what the MySQL would look like, but I need help turning it into JPQL. Here’s the equivalent SQL:

SELECT o.* FROM Observation o
LEFT JOIN Obs_Event p
ON p.Event_ID = o.Event_ID
LEFT JOIN Event_Set ppp
ON ppp.Event_ID = o.Event_ID AND ppp.Event_Set_ID = o.Event_Set_ID
WHERE o.Individual_ID = <some id>
AND o.Observation_Date = <a date value>
ORDER BY ppp.Seq_Num ASC

Any help on how to do this would be much appreciated. Specifically I seem to having trouble with this part:

ON ppp.Event_ID = o.Event_ID AND ppp.Event_Set_ID = o.Event_Set_ID

So, far I’ve tried this:

        Query q=  em.createQuery("select o " +
                " from Observation as o " +
                " join o.eventID p" +
                " join p.eventSetCollection ppp " +
                " where o.individualID = :indiv " +
                " AND o.observationDate = :d " +
                " AND o.eventID = ppp.event " +
                "";

If I try to add something like

WHERE ...
 AND o.eventSetID = ppp.eventSet 

… it simply doesn’t work. If I look at the generated SQL, it looks like ppp.eventSet is simply ignored.

Suggestions?

Answer 1

So, first thanks to the poster that commented, asking for my entity relationships. That forced me to take a closer look at things and realize what was wrong.

As it turns out, back when I was even worse at JPA than I am now, I set the o.eventID property to an actual Integer, as in the primary key of the record/object, instead of an actual object. Hence, in the JPQL above, I’m actually trying to map an object to an integer in the following statement:

AND o.eventID = ppp.event

turns out the correct statement is:

        Query q=  em.createQuery("select o " +
                " from Observation as o " +
                " join o.eventID p" +
                " join p.eventSetCollection ppp " +
                " where o.individualID = :indiv " +
                " AND o.observationDate = :d " +
                " AND o.eventID= ppp.event.eventID" +
                " order by ppp.seqNum ASC" +
                "");

This works in a pinch, although I should eventually change that relationship in the Observation class to actually go to an object.