[转]HQL基本的举例

java 代码

/*
 * 简单的查询一个表，返回List
 */
public void testHQL1(){

    Session session = factory.openSession();
    String hql = "from User";
    Query query = session.createQuery(hql);
    List<user></user> users = query.list();
    for(User user : users){
        System.out.println(user.getName());
        System.out.println("---------------");
    }

    session.close();
}


/*
 *
 * 加了一些限制的条件查询，查询得到一个List
 * 这里跟 sql 语句很像，很好！
 */
public void testHQL2(){

    Session session = factory.openSession();
    String hql = "from User where name='linweihan' and addr ='beijing'";
    Query query = session.createQuery(hql);
    List<user></user> users = query.list();
    for(User user : users){
        System.out.println(user.getName());
        System.out.println("---------------");
    }

    session.close();
}

/*
 * 排序，使用order by和sql 非常像很好
 */
public void testHQL3(){

    Session session = factory.openSession();
    String hql = "from User order by age desc";
    Query query = session.createQuery(hql);
    List<user></user> users = query.list();
    for(User user : users){
        System.out.println(user.getAge());
        System.out.println(user.getName());
        System.out.println("---------------");
    }

    session.close();
}


/*
 * 分组，使用group by
 */
public void testHQL4(){

    Session session = factory.openSession();
    String hql = "from User group by addr";
    Query query = session.createQuery(hql);
    List<user></user> users = query.list();
    for(User user : users){
        System.out.println(user.getAge());
        System.out.println(user.getName());
        System.out.println(user.getAddr());
        System.out.println("---------------");
    }

    session.close();
}


/*
 * 使用函数
 * 这里使用avg(),平均数
 * 跟sql很像啊
 */
public void testHQL5(){

    Session session = factory.openSession();
    String hql = "select avg(age) from User";
    //这里返回的List是float类型的
    Query query = session.createQuery(hql);
    List<float></float> avg_ages = query.list();
    for(Float avg_age : avg_ages){
        System.out.println(avg_age);
    }

    session.close();
}


/*
 * 分组和函数相结合
 *
 */
public void testHQL6(){

    Session session = factory.openSession();
    String hql = "select avg(age) from User group by addr";
    //这里返回的List是float类型的
    Query query = session.createQuery(hql);
    List<float></float> avg_ages = query.list();
    for(Float avg_age : avg_ages){
        System.out.println(avg_age);
    }

    session.close();
}


/*
 * 分组和函数相结合，查询平均年龄和地址
 * 所以返回的类型应该是Object
 *
 */
public void testHQL7(){

    Session session = factory.openSession();
    String hql = "select avg(age),addr from User group by addr";
    Query query = session.createQuery(hql);
    List avg_ages = query.list();
    for(Object[] avg_age : avg_ages){
        System.out.println(avg_age[1]+"----"+avg_age[0]);
    }

    session.close();
}


/*
 * 支持select 这种通用的查询
 */
public void testHQL8(){

    Session session = factory.openSession();
    String hql = "select name,age from User";
    Query query = session.createQuery(hql);
    List infos = query.list();
    for(Object[] info : infos){
        System.out.println(info[0]+"----"+info[1]);
    }

    session.close();
}

/*
 * 使用update
 * Hibernate3也支持update和delete
 * 在Hibernate2中不支持
 */
public void testHQL9(){

    Session session = factory.openSession();
    String hql = "update User set age = 100 where name = 'linweihan'";
    Query query = session.createQuery(hql);
    //需要用executeUpdate方法
    query.executeUpdate();
    //需要事务的提交才能影响数据库
    session.beginTransaction().commit();

    session.close();
}

/*
 * 使用delete
 */
public void testHQL10(){

    Session session = factory.openSession();
    String hql = "delete User where name = 'linweihan'";
    Query query = session.createQuery(hql);
    //需要用executeUpdate方法
    query.executeUpdate();
    //需要事务的提交才能影响数据库
    session.beginTransaction().commit();

    session.close();
}


/*
 * 在JDBC支持动态的参数
 * 在hibernate中也支持
 */
public void testHQL11(){

    Session session = factory.openSession();
    String hql = "from User where addr=? and age=?";
    Query query = session.createQuery(hql);
    query.setString(0, "fujian");
    query.setInteger(1, 22);
    List<user></user> users = query.list();
    for(User user : users){
        System.out.println(user.getName());
        System.out.println("---------------");
    }

    //session.close();
}


/*
 * HQL中支持这么一种的动态帮定可以起别名
 */
public void testHQL12(){

    Session session = factory.openSession();
    String hql = "from User where addr=:address and age=:age";
    Query query = session.createQuery(hql);
    query.setString("address", "fujian");
    query.setInteger("age", 22);
    List<user></user> users = query.list();
    for(User user : users){
        System.out.println(user.getName());
        System.out.println("---------------");
    }

    session.close();
}

/*
 * 另外Hibernate允许我们把 sql语句配置到文件中
 * 因为写到程序中需要编译的，而写到配置文件中是不需要编译的
 */

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hql写到配置文件当中举例 | HQL的基础

• 2007-11-30 22:15
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