count(distinct fieldName) returns number of distinct value of the table under specified field name.

Example :

package net.roseindia.main;

import net.roseindia.util.HibernateUtil;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;

public class DistinctCountHQL {
    public static void main(String[] args) {
        SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
        Session session = sessionFactory.openSession();
        String countHql = "Select count(distinct salary) FROM Employee emp";

        Query countQuery = session.createQuery(countHql);

        System.out.println("Number of Employee: " + countQuery.list().get(0));
    }
}

Output:

Hibernate: select count(distinct employee0_.salary) as col_0_0_ from employee employee0_
Number of Employee having distinct salary : 3

Description: This example counts the number of employee having distinct salary by using count(distinct salary).