获得每个部门薪资最高的员工

Question

我正在编写一个简单的HQL，以找出基于部门的薪水最高的员工。在输出中，我期待员工姓名，部门名称和最高薪水。

以下是我的实体：

Employee.java

@Entity
public class Employee implements java.io.Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int id;
    private String name;
    @ManyToOne
    @JoinColumn(name = "deptartment_id")
    private Department dept;
    @OneToOne
    @JoinColumn(name="emp_salary")
    private Salary salary;
}

Department.java

@Entity
public class Department {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int id;
    private String name;
    @OneToMany(mappedBy="dept")
    private Set<Employee> employees = new HashSet<Employee>();
}

Salary.java

@Entity
public class Salary {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int id;
    private int salary;
}

如果我在HQL查询下运行：

List<Object[]> results = session.createQuery(
                "select d.name, max(s.salary) "
                + "from Employee e join e.dept d join e.salary s "
                + "group by d.name").list();

我获得每个部门的最高薪水。这很好，但我在输出中也需要员工姓名。

所以，如果我将我的HQL更改为：

session.createQuery(
                "select e.name, d.name, max(s.salary) "
                + "from Employee e join e.dept d join e.salary s "
                + "group by d.name, e.name").list();

此查询将返回我数据库中的所有员工。

您能否告诉我什么是正确的HQL并解释我的HQL有什么问题？

这是我保存员工记录的代码：

Employee e1 = new Employee();
        e1.setName("A1");
        Salary salary1 = new Salary();
        salary1.setSalary(10000);
        e1.setSalary(salary1);
        Department dept1 = new Department();
        dept1.setName("Operations");
        e1.setDept(dept1);

        Employee e11 = new Employee();
        e11.setName("A2");
        Salary salary11 = new Salary();
        salary11.setSalary(12000);
        e11.setSalary(salary11);
        Department dept11 = new Department();
        dept11.setName("Operations");
        e11.setDept(dept11);

        Employee e12 = new Employee();
        e12.setName("A3");
        Salary salary12 = new Salary();
        salary12.setSalary(15000);
        e12.setSalary(salary12);
        Department dept12 = new Department();
        dept12.setName("Operations");
        e12.setDept(dept12);

        Employee e2 = new Employee();
        e2.setName("B1");
        Salary salary2 = new Salary();
        salary2.setSalary(20000);
        e2.setSalary(salary2);
        Department dept2 = new Department();
        dept2.setName("IT");
        e2.setDept(dept2);

        Employee e21 = new Employee();
        e21.setName("B2");
        Salary salary21 = new Salary();
        salary21.setSalary(22000);
        e21.setSalary(salary21);
        Department dept21 = new Department();
        dept21.setName("IT");
        e21.setDept(dept21);

        Employee e22 = new Employee();
        e22.setName("B3");
        Salary salary22 = new Salary();
        salary22.setSalary(25000);
        e22.setSalary(salary22);
        Department dept22 = new Department();
        dept22.setName("IT");
        e22.setDept(dept22);

        Employee e3 = new Employee();
        e3.setName("C1");
        Salary salary3 = new Salary();
        salary3.setSalary(30000);
        e3.setSalary(salary3);
        Department dept3 = new Department();
        dept3.setName("Software");
        e3.setDept(dept3);

        Employee e31 = new Employee();
        e31.setName("C2");
        Salary salary31 = new Salary();
        salary31.setSalary(32000);
        e31.setSalary(salary31);
        Department dept31 = new Department();
        dept31.setName("Software");
        e31.setDept(dept31);

        Employee e32 = new Employee();
        e32.setName("C3");
        Salary salary32 = new Salary();
        salary32.setSalary(35000);
        e32.setSalary(salary32);
        Department dept32 = new Department();
        dept32.setName("Software");
        e32.setDept(dept32);