HQL分页查询 对象导航查询外置命名查询连接查询查询过滤器统计查询

Posted 2020-08-16

分页查询

List students = session.createQuery("from Student")
                        .setFirstResult(1)
                        .setMaxResults(2)
                        .list();
            for (Iterator iter=students.iterator(); iter.hasNext();) {
                Student student = (Student)iter.next();
                System.out.println(student.getName());
            }

 

对象导航查询

session = HibernateUtils.getSession();
            session.beginTransaction();
            List students = session.createQuery("from Student s where s.classes.name like ‘%2%‘")
                        .list();
            for (Iterator iter=students.iterator(); iter.hasNext();) {
                Student student = (Student)iter.next();
                System.out.println(student.getName());
            }

 

外置命名查询

List students = session.getNamedQuery("queryStudent")
                                    .setParameter(0, 10)
                                    .list();
            for (Iterator iter=students.iterator(); iter.hasNext();) {
                Student student = (Student)iter.next();
                System.out.println(student.getName());
            }

 

连接查询

List students = session.createQuery("select c.name, s.name from Student s join s.classes c")
                        .list();
            for (Iterator iter=students.iterator(); iter.hasNext();) {
                Object[] obj = (Object[])iter.next();
                System.out.println(obj[0] + ", " + obj[1]);
            }

List students = session.createQuery("select c.name, s.name from Student s left join s.classes c")
                        .list();
            for (Iterator iter=students.iterator(); iter.hasNext();) {
                Object[] obj = (Object[])iter.next();
                System.out.println(obj[0] + ", " + obj[1]);
            }

List students = session.createQuery("select c.name, s.name from Student s right join s.classes c")
                        .list();
            for (Iterator iter=students.iterator(); iter.hasNext();) {
                Object[] obj = (Object[])iter.next();
                System.out.println(obj[0] + ", " + obj[1]);
            }

 

查询过滤器

session.enableFilter("testFilter")
                    .setParameter("myid", 10);
            List students = session.createQuery("from Student").list();
            for (Iterator iter=students.iterator(); iter.hasNext();) {
                Student student = (Student)iter.next();
                System.out.println(student.getName());
            }

 

统计查询

List list = session.createQuery("select count(*) from Student").list();
//            Long count = (Long)list.get(0);
            
            Long count = (Long)session.createQuery("select count(*) from Student").uniqueResult();
//            Long count = (Long)session.createQuery("select count(*) from Student")
//                    .setMaxResults(1)
//                    .uniqueResult();
            System.out.println("count=" + count);

String hql = "select c.name, count(s) from Classes c join c.students s group by c.name order by c.name";
            List students = session.createQuery(hql).list();
            for (int i=0; i<students.size(); i++) {
                Object[] obj = (Object[])students.get(i);
                System.out.println(obj[0] + ", " + obj[1]);
            }