HQL Hibernate INNER JOIN

如何在Hibernate中编写这个SQL查询？ 我想使用Hibernate创建查询，而不是创建数据库。

SELECT * FROM Employee e INNER JOIN Team t ON e.Id_team=t.Id_team 

我在SQLServer2008中创建了实体类，

 @Entity @Table(name="EMPLOYEE") public class Employee { @Id @GeneratedValue @Column(name="ID_EMPLOYEE") private int id_employee; @Column(name="SURNAME") private String surname; @Column(name="FIRSTNAME") private String firstname; @Column(name="ID_PROFESSION") private int id_profession; @Column(name="ID_BOSS") private int id_boss; @Column(name="HIRED_DATE") private Date hired; @Column(name="SALARY") private double salary; @Column(name="SALARY_ADD") private double salary_add; @Column(name="ID_TEAM") private int id_team; //setters and getters } @Entity @Table(name="TEAM") public class Team { @Id @GeneratedValue @Column(name="ID_TEAM") private int id_team; @Column(name="TEAMNAME") private String teamname; @Column(name="ADDRESS") private String address; //setters and getters } 

我试图以多种方式构建工作选择查询，但它仍然无效。

 SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory(); Session session = sessionFactory.openSession(); session.beginTransaction(); String select = "FROM Employee e INNER JOIN Team t ON e.Id_team=t.Id_team"; Query query = session.createQuery(select); List elist = query.list(); session.getTransaction().commit(); session.close(); 

实体可能有问题吗？

Answer 1

只有在实体之间存在关联时才能使用联接。 您的Employee实体不应该有一个名为id_team的字段，类型为int ，映射到列。 它应该与Team实体具有ManyToOne关联，映射为JoinColumn：

 @ManyToOne @JoinColumn(name="ID_TEAM") private Team team; 

然后，以下查询将完美地工作：

 select e from Employee e inner join e.team 

这将加载所有员工，除了那些与任何团队无关的员工。

当然，所有其他字段都是映射为实体的其他表的外键（ id_boss ， id_profession ）。

现在是时候阅读Hibernate文档了，因为你错过了它的一个非常重要的部分以及它是如何工作的。

Answer 2

你可以在不必创建真正的Hibernate映射的情况下完成它。 尝试这个：

 SELECT * FROM Employee e, Team t WHERE e.Id_team=t.Id_team 

Answer 3

 import java.io.Serializable; import java.util.ArrayList; import java.util.List; import javax.persistence.CascadeType; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.OneToMany; import javax.persistence.Table; @Entity @Table(name="empTable") public class Employee implements Serializable{ private static final long serialVersionUID = 1L; private int id; private String empName; List
 addList=new ArrayList
(); @Id @GeneratedValue(strategy=GenerationType.IDENTITY) @Column(name="emp_id") public int getId() { return id; } public void setId(int id) { this.id = id; } public String getEmpName() { return empName; } public void setEmpName(String empName) { this.empName = empName; } @OneToMany(mappedBy="employee",cascade=CascadeType.ALL) public List
 getAddList() { return addList; } public void setAddList(List
 addList) { this.addList = addList; } } 

我们有两个实体Employee和Address with One to Many关系。

 import java.io.Serializable; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.ManyToOne; import javax.persistence.Table; @Entity @Table(name="address") public class Address implements Serializable{ private static final long serialVersionUID = 1L; private int address_id; private String address; Employee employee; @Id @GeneratedValue(strategy=GenerationType.IDENTITY) public int getAddress_id() { return address_id; } public void setAddress_id(int address_id) { this.address_id = address_id; } public String getAddress() { return address; } public void setAddress(String address) { this.address = address; } @ManyToOne @JoinColumn(name="emp_id") public Employee getEmployee() { return employee; } public void setEmployee(Employee employee) { this.employee = employee; } } 

通过这种方式，我们可以实现两个表之间的内部连接

 import java.util.List; import org.hibernate.Query; import org.hibernate.Session; public class Main { public static void main(String[] args) { saveEmployee(); retrieveEmployee(); } private static void saveEmployee() { Employee employee=new Employee(); Employee employee1=new Employee(); Employee employee2=new Employee(); Employee employee3=new Employee(); Address address=new Address(); Address address1=new Address(); Address address2=new Address(); Address address3=new Address(); address.setAddress("1485,Sector 42 b"); address1.setAddress("1485,Sector 42 c"); address2.setAddress("1485,Sector 42 d"); address3.setAddress("1485,Sector 42 a"); employee.setEmpName("Varun"); employee1.setEmpName("Krishan"); employee2.setEmpName("Aasif"); employee3.setEmpName("Dut"); address.setEmployee(employee); address1.setEmployee(employee1); address2.setEmployee(employee2); address3.setEmployee(employee3); employee.getAddList().add(address); employee1.getAddList().add(address1); employee2.getAddList().add(address2); employee3.getAddList().add(address3); Session session=HibernateUtil.getSessionFactory().openSession(); session.beginTransaction(); session.save(employee); session.save(employee1); session.save(employee2); session.save(employee3); session.getTransaction().commit(); session.close(); } private static void retrieveEmployee() { try{ String sqlQuery="select e from Employee e inner join e.addList"; Session session=HibernateUtil.getSessionFactory().openSession(); Query query=session.createQuery(sqlQuery); List list=query.list(); list.stream().forEach((p)->{System.out.println(p.getEmpName());}); session.close(); }catch(Exception e){ e.printStackTrace(); } } } 

我使用Java 8 for循环来引用名称。 确保你有tomcat 8的jdk 1.8。还要添加一些记录以便更好地理解。

  public class HibernateUtil { private static SessionFactory sessionFactory ; static { Configuration configuration = new Configuration(); configuration.addAnnotatedClass(Employee.class); configuration.addAnnotatedClass(Address.class); configuration.setProperty("connection.driver_class","com.mysql.jdbc.Driver"); configuration.setProperty("hibernate.connection.url", "jdbc:mysql://localhost:3306/hibernate"); configuration.setProperty("hibernate.connection.username", "root"); configuration.setProperty("hibernate.connection.password", "root"); configuration.setProperty("dialect", "org.hibernate.dialect.MySQLDialect"); configuration.setProperty("hibernate.hbm2ddl.auto", "update"); configuration.setProperty("hibernate.show_sql", "true"); configuration.setProperty(" hibernate.connection.pool_size", "10"); // configuration StandardServiceRegistryBuilder builder = new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()); sessionFactory = configuration.buildSessionFactory(builder.build()); } public static SessionFactory getSessionFactory() { return sessionFactory; } }