如何使用JPQL联接两个表

如何解决如何使用JPQL联接两个表

我制作了员工表和职位表。每个员工都有一个职位。我想联接两个表，但是我不知道如何编写代码。

Employee.java

@Table(name = "employees")
@NamedQueries({
        @NamedQuery(name = "getAllEmployees",query = "SELECT e FROM Employee AS e ORDER BY e.emp_id DESC")
})
@Entity
public class Employee {
    @Id
    @Column(name = "emp_id",length = 8)
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer emp_id;

    @Column(name = "emp_name",length = 20,nullable = false)
    private String emp_name;

    @OnetoOne(cascade = CascadeType.ALL)
    @JoinTable(name = "position",joinColumns = {
            @JoinColumn(name = "emp_id",referencedColumnName = "emp_id") },inverseJoinColumns = {
                    @JoinColumn(name = "pos_id",referencedColumnName = "pos_id") })
    private Position pos;
    
    ～setter/getter～

Position.java

@Table(name = "position")

@Entity
public class Position {
    @Id
    @Column(name = "pos_id")
    private Integer pos_id;

    @Column(name = "pos_name",length = 30,nullable = false)
    private String pos_name;

    @OnetoOne(mappedBy = "pos")
    private Employee employee;
    
    ～setter/getter～

解决方法

Employee.java
@Entity
public class Employee {
    @Id
    @Column(name = "emp_id",length = 8)
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer emp_id;

    @Column(name = "emp_name",length = 20,nullable = false)
    private String emp_name;

    @ManyToOne
    private Position position;

Position.java
@Entity
public class Position {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int pos_id;

    @Column(name = "pos_name",length = 16)
    private String pos_name;

    @OneToMany(mappedBy = "position")
    private List<Employee> employees;

谢谢。我可以加入两个桌子！