Hibernate HQL示例十：统计查询

统计函数的使用

count(*) 等

package com.bjsxt.hibernate;

import java.util.Iterator;
import java.util.List;

import org.hibernate.Session;

import junit.framework.TestCase;

public class StatQueryTest extends TestCase {
	
	public void testQuery1() {
		Session session = null;
		try {
			session = HibernateUtils.getSession();
			
			//统计一
			List students = session.createQuery("select count(*) from Student").list();
			Long count = (Long)students.get(0);
			
			//统计二
			Long l = (Long)session.createQuery("select count(*) from Student").uniqueResult();
			System.out.println(count);
			System.out.println(l);
		}catch(Exception e) {
			e.printStackTrace();
		}finally {
			HibernateUtils.closeSession(session);
		}	
	}	
	
	public void testQuery2() {
		Session session = null;
		try {
			session = HibernateUtils.getSession();
			
			List students = session.createQuery("select c.id, c.name, count(s) from Student s join " +
					"s.classes c group by c.id, c.name").list();
			for (Iterator iter = students.iterator();iter.hasNext();) {
				Object[] obj = (Object[])iter.next();
				System.out.println(obj[0] + ",  " + obj[1] + ", " + obj[2]);
			}
		}catch(Exception e) {
			e.printStackTrace();
		}finally {
			HibernateUtils.closeSession(session);
		}	
	}	
	
}

 

 

注意要正确理解查询返回的list。

查询返回的list里面放的是对象数组。