JPQL supports AVG, COUNT, MAX, MIN, and SUM aggregate functions in SELECT statements.

Examples

Entity

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

Using Aggregate Functions

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

  public static void main(String[] args) {
      try {
          persistEmployees();
          findEmployeeCount();
          findEmployeeAvgSalary();
          findEmployeeMaxSalary();
          findEmployeeMinSalary();
          findEmployeeSalariesSum();

      } finally {
          entityManagerFactory.close();
      }
  }

  public static void persistEmployees() {
      Employee employee1 = Employee.create("Diana", 3000);
      Employee employee2 = Employee.create("Rose", 4000);
      Employee employee3 = Employee.create("Denise", 1500);
      Employee employee4 = Employee.create("Mike", 2000);
      EntityManager em = entityManagerFactory.createEntityManager();
      em.getTransaction().begin();
      em.persist(employee1);
      em.persist(employee2);
      em.persist(employee3);
      em.persist(employee4);
      em.getTransaction().commit();
      em.close();
  }

  private static void findEmployeeCount() {
      System.out.println("-- Employee COUNT --");
      EntityManager em = entityManagerFactory.createEntityManager();
      Query query = em.createQuery(
              "SELECT COUNT(e) FROM Employee e");
      Long result = (Long) query.getSingleResult();
      System.out.println(result);
      em.close();
  }

  private static void findEmployeeAvgSalary() {
      System.out.println("-- Employee AVG Salary --");
      EntityManager em = entityManagerFactory.createEntityManager();
      Query query = em.createQuery(
              "SELECT AVG(e.salary) FROM Employee e");
      Double result = (Double) query.getSingleResult();
      System.out.println(result);
      em.close();
  }

  private static void findEmployeeMaxSalary() {
      System.out.println("-- Employee MAX Salary --");
      EntityManager em = entityManagerFactory.createEntityManager();
      Query query = em.createQuery(
              "SELECT MAX(e.salary) FROM Employee e");
      Long result = (Long) query.getSingleResult();//salary of type long
      System.out.println(result);
      em.close();
  }

  private static void findEmployeeMinSalary() {
      System.out.println("-- Employee MIN Salary --");
      EntityManager em = entityManagerFactory.createEntityManager();
      Query query = em.createQuery(
              "SELECT MIN(e.salary) FROM Employee e");
      Long result = (Long) query.getSingleResult();//salary of type long
      System.out.println(result);
      em.close();
  }

  private static void findEmployeeSalariesSum() {
      System.out.println("-- Employee SUM Salary --");
      EntityManager em = entityManagerFactory.createEntityManager();
      Query query = em.createQuery(
              "SELECT SUM(e.salary) FROM Employee e");
      Long result = (Long) query.getSingleResult();
      System.out.println(result);
      em.close();
  }
}

-- Employee COUNT --
4
-- Employee AVG Salary --
2625.0
-- Employee MAX Salary --
4000
-- Employee MIN Salary --
1500
-- Employee SUM Salary --
10500

Example Project

Dependencies and Technologies Used:

• h2 1.4.197: H2 Database Engine.
• hibernate-core 5.2.13.Final: The core O/RM functionality as provided by Hibernate.
  Implements javax.persistence:javax.persistence-api version 2.1
• JDK 1.8
• Maven 3.3.9