Hibernate Subquery
In this section we will discuss about hibernate Subquery.
Hibernate Subquery:
Hibernate Subqueries are surrounded by parentheses ().Hibernate supports
subqueries within queries for database that support subselect.
By writing subqueries you can group, order and aggregate your resultant of query
by using where clause /in clause.
Subqueries executed before the query run.
You can write subquery by using native SQL ,HQL or Criteria.
Example : In this example we are writing subquery to find out employee whose id is equal to 3 or greater than 5.
Here is main class code -
package net.roseindia.main;
import java.util.*;
import net.roseindia.table.Employee;
import net.roseindia.util.HibernateUtil;
import org.hibernate.Criteria;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
public class MainClass {
public static void main(String[] args) {
SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
Session session = sessionFactory.openSession(); // session is opened
String hql = "SELECT emp.id, emp.name, emp.salary, emp.dateOfJoin from Employee emp " +
"WHERE emp.id IN (SELECT emp.id FROM emp Employee WHERE emp.id=3 OR emp.id>5) group by emp.id";
Query query = session.createQuery(hql);
query.setResultTransformer(Criteria.ALIAS_TO_ENTITY_MAP);
List objectList = query.list();
Iterator iterator = objectList.iterator();
System.out.println("Emp Id\tEmployee Name\tSalary\tDate of Join");
while (iterator.hasNext()) {
Map map = (Map) iterator.next();
System.out.print(map.get("0"));
System.out.print("\t" + map.get("1"));
System.out.print("\t" + map.get("2"));
System.out.print("\t" + map.get("3"));
System.out.println();
}
session.close(); // session is closed
}
}
Output:
Hibernate: select employee0_.emp_id as col_0_0_, employee0_.name as col_1_0_, employee0_.salary as col_2_0_, employee0_.date_of_join as col_3_0_ from employee employee0_ where employee0_.emp_id in (select employee0_.emp_id from employee employee0_ where employee0_.emp_id=3 or employee0_.emp_id>5) group by employee0_.emp_id Emp Id Employee Name Salary Date of Join 3 Mac 15000 2003-12-23 00:00:00.0 6 Linda 20000 2010-06-12 00:00:00.0