Hibernate查询语言HQL使用聚集函数查询。

聚集函数查询：
count(*)
avg(…)
sum(…)
min(…)
max(…)
count(…)
hql例子代码如下：
/**
* 统计查询
*/
public class StatQueryTest extends TestCase {

public void testQuery1() {
Session session = null;
try {
session = HibernateUtils.getSession();
session.beginTransaction();
Long count = (Long)session.createQuery
(“select count(*) from Student”).uniqueResult();
System.out.println(count);

session.getTransaction().commit();
}catch(Exception e) {
e.printStackTrace();
session.getTransaction().rollback();
}finally {
HibernateUtils.closeSession(session);
}
}
public void testQuery2() {
Session session = null;
try {
session = HibernateUtils.getSession();
session.beginTransaction();
List students =session.createQuery
(“select c.name, count(s) from Student s join s.classes c ”
+”group by c.name order by c.name”).list();
for (Iterator iter=students.iterator(); iter.hasNext();) {
Object[] obj = (Object[])iter.next();
System.out.println(obj[0] + “, ” + obj[1]);
}
session.getTransaction().commit();
}catch(Exception e) {
e.printStackTrace();
session.getTransaction().rollback();
}finally {
HibernateUtils.closeSession(session);
}
}
}