Query for join in Spring Data JPA

Question

I want to write a join like

Select a.id,a.desc,b.desc from A a  left join B b on a.MEDIA_ID = b.ID

I have create two Entities A & B and created CrudRepository<A,Long>.

Now, in the crudRepository in need to write a method which can get the data using the above join.

Also, i created a transient variable in entity A (Names it as 'bDescription) how to achieve this in Spring Data JPA.

Note: I need join just to find out 'description'(a column in B) for a particular id(primary key in B and mapped as 'MEDIA_ID' in A) of Entity B..

Thanks in Advance

Answer 1

Here is a sample of JOIN query with SpringData

public final static String FIND_WITH_DESC_QUERY = "SELECT a,b.desc as  bDescription " + 
                                                   "FROM A a LEFT JOIN a.descriptions b " +
                                                   "WHERE a.mediaID = :id";


@Query(FIND_WITH_DESC_QUERY)
public List<Media> findWithDescription(@Param("id") Long id);

Note :

• descriptions is the mapping of the relationship between entities A and B.
• this assume @OneToMany Set<B> descriptions()

useful link