Spring JPA - Is there a good way for inner join between entities or the only way is JPQL? - spring

Question

I have the following Entities:
#Entity
public class Organisation {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private long id;
// ...
}
#Entity
public class Section{
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private long id;
// ...
#ManyToOne
#JoinColumn(name = "organisation_id", nullable = false)
private Organisation organisation;
}
#Entity
public class SubSection {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
// ...
#ManyToOne
#JoinColumn(name = "section_id")
private Section section;
}
Now I want to find all SubSections by Organisation Id. Right now I am doing it using JPQL at the SubSectionRepository as above:
public interface SubSectionRepository extends JpaRepository<SubSection, Long>{
#Query(value = "SELECT ss.* FROM sub_section as ss INNER JOIN section as s ON ss.section_id = s.id WHERE s.organisation_id = ?1", nativeQuery = true)
List<SubSection> findByOrganisation(Long organisationId);
}
Is there any way that I can make INNER JOIN using the JpaRepository interface?

Answer 1

Did you try this way
subsectionRepository.findBySectionOrganizationId(long organizationId)

Answer 2

Update your method to
public interface SubSectionRepository extends JpaRepository<SubSection, Long> {
List<SubSection> findBySectionOrganisationId(Long organisationId);
}
Hibernate will generate something like this.
select subsec.*,
from sub_section subsec
left outer join section sec on subsection.section_id=sec.id
left outer join organisation org on section.organisation_id=org.id
where org.id=?
Don't worry about the left join term. It is actually a inner join because you have a where condition with id = on the most right table. Because of that, it effectively becomes a inner join. I.e if there is no record on the right table for that record, it will be ignored.