Question

I would like to retrieve the Reservation which has no reference ReservationInstance in DB by JPQL query. ReservationInstance entity have Reservation entity. It is OneToOne unidirectional.

Reservation Table

ID      NAME
0001    AAA
0002    BBB
0003    CCC
0004    DDD

ReservationInstance Table

ID      SOME_COLUMN     RESERVATION_ID  
0001    somedata        0004

How can I retrieve the Reservation list (For AAA, BBB and CCC) which has no ReservationInstance reference?

My Entities

public class Reservation implements Serializable {
    .....
    private String id;
    .....
    private String name;
    //getter and setter
}

public class ReservationInstance implements Serializable {
    ....
    private String id;
    ....
    private Date fromTime;
    ....
    private Date toTime;

    @OneToOne
    @JoinColumn(name = "RESERVATION_ID", referencedColumnName = "ID")
    private Reservation reservation;
}

Update Post

I used the query as below

SELECT r FROM Reservation r LEFT JOIN ReservationInstance ri WHERE ri.reservation IS NULL

I get the exception

[EL Severe]: 2012-12-18 16:37:02.817--ServerSession(1733641680)--Local Exception Stack: 
Exception [EclipseLink-8023] (Eclipse Persistence Services - 2.1.2.v20101206-r8635): org.eclipse.persistence.exceptions.JPQLException
Exception Description: Syntax error parsing the query [Reservation.findAbandonedReservation: SELECT r FROM Reservation r LEFT JOIN ReservationInstance ri WHERE ri.reservation.id IS
 NULL].
Internal Exception: org.eclipse.persistence.internal.libraries.antlr.runtime.EarlyExitException
    at org.eclipse.persistence.exceptions.JPQLException.syntaxError(JPQLException.java:352)
    at org.eclipse.persistence.internal.jpa.parsing.jpql.JPQLParser.handleRecognitionException(JPQLParser.java:350)
    at org.eclipse.persistence.internal.jpa.parsing.jpql.JPQLParser.addError(JPQLParser.java:242)
    at org.eclipse.persistence.internal.jpa.parsing.jpql.JPQLParser.reportError(JPQLParser.java:359)
    at org.eclipse.persistence.internal.jpa.parsing.jpql.antlr.JPQLParser.joinAssociationPathExpression(JPQLParser.java:11880)
    at org.eclipse.persistence.internal.jpa.parsing.jpql.antlr.JPQLParser.join(JPQLParser.java:11488)
    at org.eclipse.persistence.internal.jpa.parsing.jpql.antlr.JPQLParser.identificationVariableDeclaration(JPQLParser.java:11302)
    at org.eclipse.persistence.internal.jpa.parsing.jpql.antlr.JPQLParser.fromClause(JPQLParser.java:11164)
    at org.eclipse.persistence.internal.jpa.parsing.jpql.antlr.JPQLParser.selectStatement(JPQLParser.java:355)
    at org.eclipse.persistence.internal.jpa.parsing.jpql.antlr.JPQLParser.document(JPQLParser.java:275)
    at org.eclipse.persistence.internal.jpa.parsing.jpql.JPQLParser.parse(JPQLParser.java:130)
    at org.eclipse.persistence.internal.jpa.parsing.jpql.JPQLParser.buildParseTree(JPQLParser.java:91)
    at org.eclipse.persistence.internal.jpa.EJBQueryImpl.buildEJBQLDatabaseQuery(EJBQueryImpl.java:207)
    at org.eclipse.persistence.internal.jpa.JPAQuery.processJPQLQuery(JPAQuery.java:106)
    at org.eclipse.persistence.internal.jpa.JPAQuery.prepare(JPAQuery.java:90)
    at org.eclipse.persistence.queries.DatabaseQuery.checkPrepare(DatabaseQuery.java:509)
    at org.eclipse.persistence.queries.DatabaseQuery.checkPrepare(DatabaseQuery.java:470)
    at org.eclipse.persistence.internal.sessions.AbstractSession.processJPAQueries(AbstractSession.java:1815)
    at org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.initializeDescriptors(DatabaseSessionImpl.java:409)
    at org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.postConnectDatasource(DatabaseSessionImpl.java:666)
    at org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.loginAndDetectDatasource(DatabaseSessionImpl.java:615)
    at org.eclipse.persistence.internal.jpa.EntityManagerFactoryProvider.login(EntityManagerFactoryProvider.java:228)
    at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.deploy(EntityManagerSetupImpl.java:389)
    at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.getServerSession(EntityManagerFactoryImpl.java:164)
    at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManagerImpl(EntityManagerFactoryImpl.java:221)
    at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:209)
    at org.ace.mrbs.ost.comp.reservation.persistence.ReservationDAO.deleteAbandonedReservation(ReservationDAO.java:110)
    at org.ace.mrbs.ost.comp.reservation.persistence.ReservationDAO.main(ReservationDAO.java:130)
Caused by: org.eclipse.persistence.internal.libraries.antlr.runtime.EarlyExitException
    at org.eclipse.persistence.internal.jpa.parsing.jpql.antlr.JPQLParser.joinAssociationPathExpression(JPQLParser.java:11868)
    ... 23 more

Answer 1

MY first choice would be to make the relation Bi-Directional.

Turns out LEFT JOIN with ON will only be supported in JPA 2.1 so I suggest something like this:

SELECT r FROM Reservation r WHERE r IS NOT IN (SELECT ri.reservation FROM ReservationInstance ri)

Not 100% sure this works, if not try using r.id IS NOT IN some query the returns the ids.