How to write a JPA request

Question

Learning how to write a JPA request. Please tell me if it is possible to write the following queries more efficiently, maybe in one select statement. Maybe join, but not sure how to do it.

class Relationship {

  @ManyToOne
  public String relationshipType;  //can be MANAGER, CUSTOMER etc

  @ManyToOne
  public Party partyFrom; // a person who has a relation

  @ManyToOne
  public Party partyTo; // a group a person relate to
}

Inquiries

        String sql = "";
        sql = "select rel.partyTo";
        sql += " from Relationship rel";
        sql += " where rel.partyFrom = :partyFrom";
        sql += " and rel.relationshipType= :typeName";
        Query query = Organization.em().createQuery(sql);
        query.setParameter("partyFrom", mgr1);
        query.setParameter("typeName", "MANAGER");
        List<Party> orgList = query.getResultList();

        String sql2 = "";
        sql2 = "select rel.partyFrom";
        sql2 += " from Relationship rel";
        sql2 += " where rel.partyTo = :partyToList";
        sql2 += " and rel.relationshipType = :typeName2";
        Query query2 = Organization.em().createQuery(sql2);
        query2.setParameter("partyToList", orgList);
        query2.setParameter("typeName2", "CUSTOMER");
        List<Party> personList2 = query2.getResultList();

Both requests work. Query 1 returns a list of groups in which the person (mgr1) has a relationship of MANAGER s. Query 2 returns all the persons to which they belong to the groups returned by query 1. In fact, I get a list of the Persons to whom they belong (the client) of the same group where Person (mgr1) is related to MANAGER c.

Is it possible to combine them into one SQL query, perhaps only one db access?

Answer 1

" ", , .

select rel2.partyFrom
from Relationship rel2
where rel2.relationshipType = :typeName2 /* customer */
and rel2.partyTo.id in 
      (select rel.partyTo.id
      from Relationship rel
      where rel.partyFrom = :partyFrom
      and rel.relationshipType = :typeName)

typeName, typeName2 partyFrom, . PartyTo , ( .)

, , where, , , "in" .

EDIT: .id , , , .

Answer 2

, , - @OneToMany Spring Data JPA JPQL, JPA, 2-,

@Entity
@Table(name = "MY_CAR")
public class MyCar {

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;

@Column(name = "DESCRIPTION")
private String description;

@Column(name = "MY_CAR_NUMBER")
private String myCarNumber;

@Column(name = "RELEASE_DATE")
private Date releaseDate;

@OneToMany(cascade = { CascadeType.ALL })
@JoinTable(name = "MY_CAR_VEHICLE_SERIES", joinColumns = @JoinColumn(name = "MY_CAR_ID "), inverseJoinColumns = @JoinColumn(name = "VEHICLE_SERIES_ID"))
private Set<VehicleSeries> vehicleSeries;
public MyCar() {
    super();
    vehicleSeries = new HashSet<VehicleSeries>();
}
// set and get method goes here


@Entity
@Table(name = "VEHICLE_SERIES ")
public class VehicleSeries {

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;

@Column(name = "SERIES_NUMBER")
private String seriesNumber;

@OneToMany(cascade = { CascadeType.ALL })
@JoinTable(name = "VEHICLE_SERIES_BODY_TYPE", joinColumns = @JoinColumn(name = "VEHICLE_SERIES_ID"), inverseJoinColumns = @JoinColumn(name = "BODY_TYPE_ID"))
private Set<BodyType> bodyTypes;
public VehicleSeries() {
    super();
    bodyTypes = new HashSet<BodyType>();
}
// set and get method goes here


@Entity
@Table(name = "BODY_TYPE ")
public class BodyType implements Serializable {

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;

@Column(name = "NAME")
private String name;
// set and get method goes here


public interface MyCarRepository extends JpaRepository<MyCar, Long> {
public Set<MyCar> findAllByOrderByIdAsc();

@Query(value = "select distinct myCar from MyCar myCar "
        + "join myCar.vehicleSeries as vs join vs.bodyTypes as bt where vs.seriesNumber like %:searchMyCar% "
        + "or lower(bt.name) like lower(:searchMyCar) or myCar.bulletinId like %:searchMyCar% "
        + "or lower(myCar.description) like lower(:searchMyCar) "
        + "or myCar.bulletinNumber like %:searchMyCar% order by myCar.id asc")
public Set<MyCar> searchByMyCar(@Param("searchMyCar") String searchMyCar);

}

* Vehicle_Series

ID      SERIES_NUMBER  
1       Yaris
2       Corolla

* Body_Type

ID      NAME  
1       Compact
2       Convertible 
3       Sedan