如何使用 LEFT JOIN 創建 JPA NamedQuery

Question

我有兩個實體：汽車和預訂。 我想用 LEFT JOIN 創建命名查詢。 我試圖像這里描述的那樣做這件事How to create JPA query with LEFT OUTER JOIN但它不起作用。 你知道我的查詢有什么問題嗎？ 我想展示保留為 NULL 的汽車。 無論如何，即使使用 JOIN 它也不起作用。 啟動應用程序后，我有一個錯誤：

Caused by: org.hibernate.HibernateException: Errors in named queries: Car.findAll
    at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:495) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:444) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:879) ~[hibernate-entitymanager-5.0.12.Final.jar:5.0.12.Final]
    ... 22 common frames omitted

原則上我想實現這個在 MySQL 中有效的查詢

SELECT distinct * FROM car c LEFT JOIN reservation r ON c.id = r.car_id WHERE c.producer='producer' AND c.model='model' AND c.type='type' 
AND (r.date_of_rent < 'date1' AND r.date_of_return < 'date1') OR (r.date_of_rent > 'date2') OR r.date_of_rent IS NULL;

汽車實體

import java.io.Serializable;
import java.util.List;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.NamedQuery;
import javax.persistence.OneToMany;

@Entity
@NamedQuery(name = "Car.findAll", query = "SELECT c FROM Car c LEFT JOIN c.reservation r WHERE c.producer=:producer "
        + "AND c.type=:type AND c.dailyPrice=:dailyPrice")
public class Car implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String producer;
    private String model;
    private int seatsNumber;
    private String type;
    private String registrationNumber;
    private double dailyPrice;
    private String description;
    @OneToMany(mappedBy = "car")
    private List<Reservation> reservations;

預訂實體

import java.io.Serializable;
import java.sql.Date;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.ManyToOne;

@Entity
public class Reservation implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @ManyToOne
    private User user;
    @ManyToOne
    private Car car;
    private Date dateOfRent;
    private Date dateOfReturn;

非常感謝您的幫助。

更新

問題解決了。 查詢應如下所示

import java.io.Serializable;
import java.util.List;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.NamedQuery;
import javax.persistence.OneToMany;

@Entity
@NamedQuery(name = "Car.findAll", query = "SELECT DISTINCT c FROM Car c LEFT JOIN c.reservations r WHERE "
        + "c.type=:type AND c.dailyPrice<=:dailyPrice AND ((r.dateOfRent < :dateOfRent AND r.dateOfReturn < :dateOfRent) OR "
        + "(r.dateOfRent > :dateOfReturn) OR (r.dateOfRent IS NULL))")
public class Car implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String producer;
    private String model;
    private Integer seatsNumber;
    private String type;
    private String registrationNumber;
    private Double dailyPrice;
    private String description;
    @OneToMany(mappedBy = "car")
    private List<Reservation> reservations;

Answer 1

SELECT c FROM Car c LEFT JOIN c.reservation r WHERE c.producer=:producer "
        + "AND c.type=:type AND c.dailyPrice=:dailyPrice

此查詢有錯誤c.reservation需要更改為c.reservations 。

我想展示保留為 NULL 的汽車。

你不能這樣做。 嘗試從這個查詢開始：

select c from Car c where not exists (
    select r.id from Reservation r where r.car.id = c.id
)