Hibernate的hql查询语句详细总结

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/Speed_Pig/article/details/72991095

   Hql即Hibernate Query Language,是一个面向对象的查询语言，是基于对象进行查询的，不是基于数据库中表，字段的。

1、准备

首先有两个类TBook类和Category类，两者之间是多对一的关系。

两个类对应两张表，我们先保存一些数据。

@Test
public void save() {
    Session session = null;
    Transaction tran = null;

    try {
        session = SessionUtil.getSession();
        tran = session.beginTransaction();
        Category c1 = new Category();
        c1.setCategory("文学");

        Category c2 = new Category();
        c2.setCategory("历史");

        Category c3 = new Category();
        c3.setCategory("武侠");

        Category c4 = new Category();
        c4.setCategory("科幻");

        Category c5 = new Category();
        c5.setCategory("言情");

        TBook book1 = new TBook();
        book1.setBName("红楼梦");
        book1.setAuthor("曹雪芹");
        book1.setBPrice(60);
        book1.setPubDate(new Date());
        book1.setCategory(c1);

        TBook book2 = new TBook();
        book2.setBName("资治通鉴");
        book2.setAuthor("司马光");
        book2.setBPrice(63);
        book2.setPubDate(new Date());
        book2.setCategory(c2);

        TBook book3 = new TBook();
        book3.setBName("射雕英雄传");
        book3.setAuthor("金庸");
        book3.setBPrice(73);
        book3.setPubDate(new Date());
        book3.setCategory(c3);

        TBook book4 = new TBook();
        book4.setBName("百年孤独");
        book4.setAuthor("马尔克斯");
        book4.setBPrice(56);
        book4.setPubDate(new Date());
        book4.setCategory(c4);

        TBook book5 = new TBook();
        book5.setBName("傲慢与偏见");
        book5.setAuthor("简奥斯丁");
        book5.setBPrice(60);
        book5.setPubDate(new Date());
        book5.setCategory(c5);

        TBook book6 = new TBook();
        book6.setBName("西游记");
        book6.setAuthor("罗贯中");
        book6.setBPrice(68);
        book6.setPubDate(new Date());
        book6.setCategory(c1);

        session.save(book1);
        session.save(book2);
        session.save(book3);
        session.save(book4);
        session.save(book5);
        session.save(book6);

        tran.commit();

    } catch (Exception ex) {
        ex.printStackTrace();
    } finally {
        session.close();
    }
}

表中详细数据

2、Hql查询

2.1、查询单一属性

@Test
public void query1(){
    Session session = null;
    try {
        session = SessionUtil.getSession();

        List<String> list = session.createQuery("select BName from TBook").list();
        for (String name : list) {
            System.out.println(name);
        }
    } catch (Exception e) {
        e.printStackTrace();
    }finally{
        SessionUtil.close(session);
    }
}

红楼梦
资治通鉴
射雕英雄传
百年孤独
傲慢与偏见
西游记

2.2、返回多个属性的查询

@Test
public void query2(){
    Session session = null;
    try {
        session = SessionUtil.getSession();
        List<Object[]> list = session.createQuery("select BName,BPrice from TBook")
                            .list();
        for(Object[] book : list){
            System.out.println("书名："+book[0]+"\t\t价格："+book[1]);
        }
    } catch (Exception e) {
        e.printStackTrace();
    }finally{
        SessionUtil.close(session);
    }
}

书名：红楼梦      价格：60
书名：资治通鉴     价格：63
书名：射雕英雄传    价格：73
书名：百年孤独     价格：56
书名：傲慢与偏见    价格：60
书名：西游记      价格：68

注意查询多个属性的时候，查询到的是一个对象数据的集合。

另一种方式

@Test
    public void query3(){
        Session session = null;
        try {
            session = SessionUtil.getSession();
            List<TBook> list = session.createQuery("select new TBook(BName,BPrice) from TBook").list();
            for(TBook book : list){
                System.out.println(book.getBName()+"---"+book.getBPrice());
            }

        } catch (Exception e) {
            e.printStackTrace();
        }finally{
            SessionUtil.close(session);
        }
    }

既然Hql中用到了new TBook(BName,BPrice)，那么你的pojo类中必然要有一个这样的构造函数。

2.3、查询全部属性

@Test
public void query3(){
    Session session = null;
    try {
        session = SessionUtil.getSession();
        List<TBook> list = session.createQuery("from TBook").list();
        for(TBook book : list){
            System.out.println(book);
        }
    } catch (Exception e) {
        e.printStackTrace();
    }finally{
        SessionUtil.close(session);
    }
}

TBook [id=1, author=曹雪芹, BName=红楼梦, BPrice=60, pubDate=2017-06-10 14:51:57.0]
TBook [id=2, author=司马光, BName=资治通鉴, BPrice=63, pubDate=2017-06-10 14:51:57.0]
TBook [id=3, author=金庸, BName=射雕英雄传, BPrice=73, pubDate=2017-06-10 14:51:57.0]
TBook [id=4, author=马尔克斯, BName=百年孤独, BPrice=56, pubDate=2017-06-10 14:51:57.0]
TBook [id=5, author=简奥斯丁, BName=傲慢与偏见, BPrice=60, pubDate=2017-06-10 14:51:57.0]
TBook [id=6, author=罗贯中, BName=西游记, BPrice=68, pubDate=2017-06-10 14:51:57.0]

其中hql也可以写完整的，那样要使用别名，即select t from TBook t

2.4、条件查询之拼接查询语句

@Test
public void query4(){
    Session session = null;
    try {
        session = SessionUtil.getSession();
        List<TBook> list = session.createQuery("from TBook where id<"+4).list();            
        for(TBook book : list){
            System.out.println(book);           }
    } catch (Exception e) {
        e.printStackTrace();
    }finally{
        SessionUtil.close(session);
    }
}

2.5、条件查询之占位符方式

@Test
public void query5(){
    Session session = null;
    try {
        session = SessionUtil.getSession();
        List<TBook> list = session.createQuery("from TBook where id<?")
                            .setInteger(0,3).list();
        for(TBook book : list){
            System.out.println(book);
        }

    } catch (Exception e) {
        e.printStackTrace();
    }finally{
        SessionUtil.close(session);
    }
}

注意下表从0开始

此后的查询结果不再罗列。

2.6、条件查询之基于别名的查询

@Test
public void query6(){
    Session session = null;
    try {
        session = SessionUtil.getSession();
        List<TBook> list = session.createQuery("from TBook where id<:id")
                .setParameter("id",4).list();
        for(TBook book : list){
            System.out.println(book);
        }
    } catch (Exception e) {
        e.printStackTrace();
    }finally{
        SessionUtil.close(session);
    }
}

2.7、分页查询

只需要设置起始位置和最大的查询数据个数即可，注意不包括设置的起始位置。

@Test
public void query7(){
    Session session = null;
    try {
        session = SessionUtil.getSession();
        List<TBook> list = session.createQuery("from TBook")
                .setFirstResult(0).setMaxResults(4).list();
        for(TBook book : list){
            System.out.println(book);
        }
    } catch (Exception e) {
        e.printStackTrace();
    }finally{
        SessionUtil.close(session);
    }
}

结果：

TBook [id=1, author=曹雪芹, BName=红楼梦, BPrice=60, pubDate=2017-06-10 14:51:57.0]
TBook [id=2, author=司马光, BName=资治通鉴, BPrice=63, pubDate=2017-06-10 14:51:57.0]
TBook [id=3, author=金庸, BName=射雕英雄传, BPrice=73, pubDate=2017-06-10 14:51:57.0]
TBook [id=4, author=马尔克斯, BName=百年孤独, BPrice=56, pubDate=2017-06-10 14:51:57.0]

2.8、聚合查询之count

@Test
public void query8(){
    Session session = null;
    try {
        session = SessionUtil.getSession();
        //Object count = session.createQuery("select count(*) from TBook").uniqueResult();
        Number count = (Number)session.createQuery("select count(*) from TBook").uniqueResult();
        System.out.println(count.intValue());
    } catch (Exception e) {
        e.printStackTrace();
    }finally{
        SessionUtil.close(session);
    }
}

2.9、聚合查询之avg

@Test
public void query9(){
    Session session = null;
    try {
        session = SessionUtil.getSession();
        Number priceavg = (Number)session.createQuery("select avg(BPrice) from TBook").uniqueResult();
        System.out.println(priceavg.doubleValue());
    } catch (Exception e) {
        e.printStackTrace();
    }finally{
        SessionUtil.close(session);
    }
}

2.10、排序查询

@Test
public void query10(){
    Session session = null;
    try {
        session = SessionUtil.getSession();
        List<TBook> list = session.createQuery("from TBook order by BPrice").list();
        for(TBook book : list){
            System.out.println(book);
        }
    } catch (Exception e) {
        e.printStackTrace();
    }finally{
        SessionUtil.close(session);
    }
}

结果：

TBook [id=4, author=马尔克斯, BName=百年孤独, BPrice=56, pubDate=2017-06-10 14:51:57.0]
TBook [id=1, author=曹雪芹, BName=红楼梦, BPrice=60, pubDate=2017-06-10 14:51:57.0]
TBook [id=5, author=简奥斯丁, BName=傲慢与偏见, BPrice=60, pubDate=2017-06-10 14:51:57.0]
TBook [id=2, author=司马光, BName=资治通鉴, BPrice=63, pubDate=2017-06-10 14:51:57.0]
TBook [id=6, author=罗贯中, BName=西游记, BPrice=68, pubDate=2017-06-10 14:51:57.0]
TBook [id=3, author=金庸, BName=射雕英雄传, BPrice=73, pubDate=2017-06-10 14:51:57.0]

2.11、分组查询

@Test
public void query11(){
    Session session = null;
    try {
        session = SessionUtil.getSession();
        List<Object[]> list = session.createQuery("select t.category.category,count(t.BName) from TBook t "
                + "group by t.category.category").list();

        for (Object[] book : list) {
            System.out.println(book[0]+"-----"+book[1]);
        }
    } catch (Exception e) {
        e.printStackTrace();
    }finally{
        SessionUtil.close(session);
    }
}

结果：

历史-----1
文学-----2
武侠-----1
科幻-----1
言情-----1