HQL Group By Clause Example

Student.java

package com.sdnext.hibernate.tutorial.dto;

import java.io.Serializable;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="STUDENT")
public class Student implements Serializable 
{

 /**
  * serialVersionUID
  */
 private static final long serialVersionUID = 8633415090390966715L;
 @Id
 @Column(name="ID")
 @GeneratedValue(strategy=GenerationType.AUTO)
 private int id;
 @Column(name="STUDENT_NAME")
 private String studentName;
 @Column(name="ROLL_NUMBER")
 private int rollNumber;
 @Column(name="COURSE")
 private String course;
 public int getId() {
  return id;
 }
 public void setId(int id) {
  this.id = id;
 }
 public String getStudentName() {
  return studentName;
 }
 public void setStudentName(String studentName) {
  this.studentName = studentName;
 }
 public int getRollNumber() {
  return rollNumber;
 }
 public void setRollNumber(int rollNumber) {
  this.rollNumber = rollNumber;
 }
 public String getCourse() {
  return course;
 }
 public void setCourse(String course) {
  this.course = course;
 }
}

hibernate.cfg.xml

<?xml version="1.0" encoding="UTF-8"?>

<?DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration> 
 <session-factory> 
  <!-- Database connection settings -->
   <property name="connection.driver_class">com.mysql.jdbc.Driver</property> 
   <property name="connection.url">jdbc:mysql://localhost:3306/hibernateDB2</property> 
   <property name="connection.username">root</property> 
   <property name="connection.password">root</property> 

  <!-- JDBC connection pool (use the built-in) -->
   <property name="connection.pool_size">1</property> 

  <!-- SQL dialect -->
   <property name="dialect">org.hibernate.dialect.MySQLDialect</property> 

  <!-- Enable Hibernate's automatic session context management -->
    <property name="current_session_context_class">thread</property> 
  
  <!-- Disable the second-level cache -->
   <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property> 

  <!-- Echo all executed SQL to stdout -->
   <property name="show_sql">true</property> 
  
  <!-- Drop and re-create the database schema on startup -->
   <property name="hbm2ddl.auto">update</property> 
   
   
   <mapping class="com.sdnext.hibernate.tutorial.dto.Student"/>
      
  </session-factory> 
 </hibernate-configuration>

HibernateTestDemo.java

package com.sdnext.hibernate.tutorial;

import java.util.Iterator;

import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.AnnotationConfiguration;

public class HibernateTestDemo {
 /**
  * @param args
  */
 public static void main(String[] args) 
 {
  SessionFactory sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory();
  Session session = sessionFactory.openSession();
  session.beginTransaction();
  
  String SQL_QUERY = "SELECT student.course, COUNT(student.course) FROM Student student GROUP BY student.course";
  Query query = session.createQuery(SQL_QUERY);
    
  for(Iterator it=query.iterate();it.hasNext();)
  {
   Object[] row = (Object[]) it.next();
   System.out.print("Course Name: " + row[0]);
   System.out.println(" | Number of Students: " + row[1]);
  }
  session.getTransaction().commit();
  session.close();
 }
}