Hibernate4.3 HQL查询

HQL：Hibernate专属语言，可以跨数据库

一、基本查询

public void testQuery(){
        Session session = HibernateUtils.getSession();
        String hql = "from Person";
        Query query = session.createQuery(hql);
        List<Person> list = query.list();
        for(Person p : list){
            System.out.println(p);
        }
        HibernateUtils.close(session);
    }

　　单个属性列查询

//查询单个属性
        String hql = "select p.pname from Person p";
        Query query = session.createQuery(hql);
        List<String> list = query.list();

　　多个属性查询

//查询多列
        String hql = "select p.id,p.pname from Person p";
        Query query = session.createQuery(hql);
        List<Object[]> objArrList = query.list();
        for(Object[] objArr : objArrList){
            System.out.println("编号："+objArr[0]+"   姓名："+objArr[1]);
        }

二、Hibernate分页查询

Session session = HibernateUtils.getSession();
        String hql = "from Person";
        Query query = session.createQuery(hql);
        //设置分页查询
        query.setFirstResult(0);
        query.setMaxResults(5);
        List<Person> list = query.list();

三、限定查询

String hql = "from Person  where id = ?";
        Query query = session.createQuery(hql);
        query.setParameter(0, 5);
        List<Person> list = query.list();

Session session = HibernateUtils.getSession();
        String hql = "from Person  where id = :id";
        Query query = session.createQuery(hql);
        query.setParameter("id", 5);
        List<Person> list = query.list();

四、统计查询

String hql = "select count(*) from Person p";
        Query query = session.createQuery(hql);
        Object result =  query.uniqueResult();

五、分组统计查询

String hql = "select avg(p.salary),p.pgender from Person p group by p.pgender";
        Query query = session.createQuery(hql);
        List<Object[]> objArrList = query.list();

六、投影查询

建立一个业务Bean,在bean提供有参的构造器来接收sql的返回值，创建出对象

七、排序查询

String hql = "from Person p order by p.salary desc";
        Query query = session.createQuery(hql);
        List<Person> list = query.list();

八、从配置文件中设置查询，然后提取

在 Person.hbm.xml配置文件中
1 <query name="getPerson">
        <![CDATA[
            from Person p where p.salary > 400
        ]]>
    </query>

Query query = session.getNamedQuery("getPerson");
        List<Person> list = query.list();