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I'm writing a JPQL query that joins across three tables. In my resultlist I would like to get all three entities per matching row (hope that makes sense).
Any ideas?
Hibernate 3.x is my JPA provider.
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3.1. In order to create a query returning multiple different entities, we need to do 2 things. Firstly, we need to list entities that we want to return in the SELECT part of the SQL Query, separated by a comma. Secondly, we need to connect them with each other by their primary and corresponding foreign keys.
Basically what you are looking for is batch insert into database using JPA. These topics have already been brought up, these will help you: JPA/Hibernate bulk(batch) insert. Batch inserts with JPA/EJB3.
The only way to join two unrelated entities with JPA 2.1 and Hibernate versions older than 5.1, is to create a cross join and reduce the cartesian product in the WHERE statement. This is harder to read and does not support outer joins. Hibernate 5.1 introduced explicit joins on unrelated entities.
Load multiple entities by their primary key class ); List<PersonEntity> persons = multiLoadAccess. multiLoad(1L, 2L, 3L); You just need to call the byMultipleIds(Class entityClass) method on the Hibernate Session and provide the class of the entities you want to load as a parameter.
IIRC, you can do a SELECT o1, o2, o3 FROM EntityA o1, EntityB o2, EntityC o3 WHERE ...., and the result will be a List<Object[3]>, where the array contents will contain the o1,o2,o3 values.
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