使用哪个联接操作将多个表与JPA / SQL查询结合在一起？

Question

I have a JPA database setup like the following:

@Entity
public class Contact {

    @Id
    private Long id;
    @Column(length = 64)
    private String firstname;
    @Column(length = 64)
    private String surname;

    @OneToMany(mappedBy = "contact") 
    private List<Address> adresses = new ArrayList<Address>();
    @OneToMany(mappedBy = "contact") 
    private List<Telephone> telephones = new ArrayList<Telephone>();

}

@Entity
public class Address {

    @Id
    private Long id;
    @Column(length = 128)
    private String street;
    @Column(length = 16)
    private String plz;


    @ManyToOne 
    private Contact contact;

}

@Entity
public class Telephone {

    @Id
    private Long id;
    @Column(length = 32)
    private String number;


    @ManyToOne
    private Contact contact;

}

Now I have the following query for my search form:

em.createQuery("SELECT DISTINCT c FROM Contact c LEFT JOIN c.addresses a LEFT JOIN c.telephones t "
                        + "WHERE c.surnameLIKE '%"+var_surname+"%' "
                        + "AND c.firstname LIKE '%"+var_firstname+"%' "
                        + "AND a.street LIKE '%"+var_street+"%'"
                        + "AND t.nummer LIKE '%"+var_telephone+"%'"
                        ).getResultList();

My question is now how can I join all 3 tables in a single JPA-query to look up for the firstname, street and number for example? I tried already with LEFT JOIN, but I don't get any results when for example the Telephone table is empty (it properly works if all tables have appropriate entries). I would like to have a result list with the Contacts even when there are no phone numbers and just one result even if a contact has more than one phone number for example.

Many thanks for your help in advance.

Answer 1

Did you try using "LEFT OUTER JOIN" eg below?

           "SELECT DISTINCT c FROM Contact c LEFT OUTER JOIN c.addresses a LEFT OUTER JOIN c.telephones t "
          + "WHERE c.surnameLIKE '%"+var_surname+"%' "
          + "AND c.firstname LIKE '%"+var_firstname+"%' "
          + "AND a.street LIKE '%"+var_street+"%'"
          + "AND t.nummer LIKE '%"+var_telephone+"%'"
          ).getResultList();

Answer 2

The DISTINCT should remove the duplicates,

for getting results if there is no relationship you need to use an OR,

      + "AND ((a.id is null) OR (a.street LIKE '%"+var_street+"%'))"

Answer 3

Thanks for your helpful answers. Finally I had to solve the problem with a dynamic buildup of my search string, selectively add/remove some parts of the join operands depending on which fields the user left empty.

    public List<Person> querySearch(String snachname, String svorname, String srechtsform, String sadresse, String sort, String sland, String stelefon, String semail, LoadGroup group) {
        if(srechtsform.equals("Alle")) {
            srechtsform = "";
        }
        if(sland.equals("Alle")) {
            sland = "";
        }
        String q = "SELECT DISTINCT * FROM Person p LEFT OUTER JOIN Adresse a ON (a.PERSON_ID=p.ID) LEFT OUTER JOIN Telefon t ON (t.PERSON_ID=p.ID) LEFT OUTER JOIN Email e ON (e.PERSON_ID=p.ID) WHERE p.nachname1 LIKE '%"+snachname+"%'AND p.vorname LIKE '%"+svorname+"%' AND p.rechtsform LIKE '%"+srechtsform+"%' ";
        if(sadresse.equals("") && sort.equals("") && sland.equals("")) {
            q += "AND (a.ID IS NULL OR (a.strasse LIKE '%"+sadresse+"%' AND a.ort LIKE '%"+sort+"%' AND a.land LIKE '%"+sland+"%')) "; 
        } else {
            q += "AND a.strasse LIKE '%"+sadresse+"%' AND a.ort LIKE '%"+sort+"%' AND a.land LIKE '%"+sland+"%' "; 
        }
        if(stelefon.equals("")) {
            q += "AND (t.ID IS NULL OR t.nummer LIKE '%"+stelefon+"%') ";
        } else {
            q += "AND t.nummer LIKE '%"+stelefon+"%' ";
        }
        if(semail.equals("")) {
            q += "AND (e.ID IS NULL OR e.mailadresse LIKE '%"+semail+"%') ";
        } else {
            q += "AND e.mailadresse LIKE '%"+semail+"%' ";
        }
        q += "GROUP BY p.ID";
        Query query = em.createNativeQuery(q, Person.class);
        if(group!=null) { query.setHint(QueryHints.LOAD_GROUP, group); }
        return query.getResultList();
    }

Answer 4

"LEFT OUTER JOIN a ON b" style syntax is not supported in JPA (see http://chrisiecorner.blogspot.fi/2012/12/jpa-and-outer-joins.html )

You must do native query.