JPQL DELETE queries can be used to delete entity objects in database. Following is the general syntax:

DELETE FROM entity_name [[AS] identification_variable] [where_clause] 

DELETE queries can only be executed in a transaction and the changes are only visible to other users after commit.

Example

Entity

@Entity
public class Employee {
    @Id
    @GeneratedValue
    private long id;
    private String name;
    private double salary;
    private String dept;
    .............
}

Executing DELETE query

public class ExampleMain {
    private static EntityManagerFactory entityManagerFactory =
            Persistence.createEntityManagerFactory("example-unit");

    public static void main(String[] args) {
        try {
            persistEmployees();
            findAllEmployees();
            deleteEmployeeByName();
            findAllEmployees();
            deleteAllEmployees();
            findAllEmployees();
        } finally {
            entityManagerFactory.close();
        }
    }

    public static void persistEmployees() {
        Employee employee1 = Employee.create("Diana", 2000, "IT");
        Employee employee2 = Employee.create("Rose", 3500, "Admin");
        Employee employee3 = Employee.create("Denise", 2500, "Admin");
        Employee employee4 = Employee.create("Mike", 4000, "IT");
        Employee employee5 = Employee.create("Linda", 4500, "Sales");
        EntityManager em = entityManagerFactory.createEntityManager();
        em.getTransaction().begin();
        em.persist(employee1);
        em.persist(employee2);
        em.persist(employee3);
        em.persist(employee4);
        em.persist(employee5);
        em.getTransaction().commit();
        em.close();
    }

    private static void findAllEmployees() {
        EntityManager em = entityManagerFactory.createEntityManager();
        System.out.println("-- All employees --");
        Query query = em.createQuery(
                "SELECT e FROM Employee e");
        List<Employee> resultList = query.getResultList();
        System.out.println("Employees count: "+resultList.size());
        resultList.forEach(System.out::println);
        em.close();
    }

    private static void deleteEmployeeByName() {
        System.out.println("-- delete employee by name 'Mike' --");
        EntityManager em = entityManagerFactory.createEntityManager();
        em.getTransaction().begin();
        Query query = em.createQuery("DELETE FROM Employee e WHERE e.name = :employeeName ");
        query.setParameter("employeeName", "Mike");
        int rowsDeleted = query.executeUpdate();
        System.out.println("entities deleted: " + rowsDeleted);
        em.getTransaction().commit();
        em.close();
    }

    private static void deleteAllEmployees() {
        System.out.println("-- delete all employees --");
        EntityManager em = entityManagerFactory.createEntityManager();
        em.getTransaction().begin();
        Query query = em.createQuery("DELETE FROM Employee e ");
        int rowsDeleted = query.executeUpdate();
        System.out.println("entities deleted: " + rowsDeleted);
        em.getTransaction().commit();
        em.close();
    }
}

-- All employees --
Employees count: 5
Employee{id=1, name='Diana', salary=2000.0, dept='IT'}
Employee{id=2, name='Rose', salary=3500.0, dept='Admin'}
Employee{id=3, name='Denise', salary=2500.0, dept='Admin'}
Employee{id=4, name='Mike', salary=4000.0, dept='IT'}
Employee{id=5, name='Linda', salary=4500.0, dept='Sales'}
-- delete employee by name 'Mike' --
entities deleted: 1
-- All employees --
Employees count: 4
Employee{id=1, name='Diana', salary=2000.0, dept='IT'}
Employee{id=2, name='Rose', salary=3500.0, dept='Admin'}
Employee{id=3, name='Denise', salary=2500.0, dept='Admin'}
Employee{id=5, name='Linda', salary=4500.0, dept='Sales'}
-- delete all employees --
entities deleted: 4
-- All employees --
Employees count: 0

Example Project

Dependencies and Technologies Used:

• h2 1.4.197: H2 Database Engine.
• hibernate-core 5.3.1.Final: Hibernate's core ORM functionality.
  Implements javax.persistence:javax.persistence-api version 2.2
• JDK 1.8
• Maven 3.5.4