一、概述

检索方式:查询的方式

导航对象图检索方式: 根据已经加载的对象导航到其他对象

Customer customer = (Customer)session.get(Customer.class,1);

customer.getOrders();// 获得到客户的订单

OID 检索方式: 按照对象的 OID 来检索对象

get()/load();方法进行检索.

HQL 检索方式: 使用面向对象的 HQL 查询语言

Query query = session.createQuery(“HQL”);

QBC 检索方式: 使用 QBC(Query By Criteria) API 来检索对象. 这种 API 封装了基于字符串形式的查询语句, 提供了更加面向对象的查询接口.

Criteria criteria = session.createCriteria(Customer.class);

本地 SQL 检索方式: 使用本地数据库的 SQL 查询语句

SQLQuery query = session.createSQLQuery(“SQL”);

二、HQL 2.1 简介

HQL:Hibernate Query Language

特点:

面向对象的查询

支持方法链编程

使用:

创建Query接口

2.2 查询所有记录 List<Customer> list = session.createQuery("from Customer").list(); for (Customer customer : list) { System.out.println(customer); } 2.3 查询使用别名 // 使用别名 // 别名as可以省略 /* List<Customer> list = session.createQuery("from Customer c").list(); System.out.println(list);*/ // 使用别名:带参数 /*List<Customer> list = session .createQuery("from Customer as c where c.cname = ?") .setString(0, "小沈").list(); System.out.println(list);*/ // 不支持 select * from Customer写法.可以写成 select 别名 from Customer as 别名; List<Customer> list = session.createQuery("select c from Customer c").list(); System.out.println(list); 2.4 排序 List<Customer> list = session.createQuery( "from Customer c order by c.id desc").list(); for (Customer customer : list) { System.out.println(customer); } 2.5 分页查询 Query query = session.createQuery("from Order"); query.setFirstResult(20); query.setMaxResults(10); List<Order> list = query.list(); for (Order order : list) { System.out.println(order); } 2.6 单个对象查询 Customer customer = (Customer) session .createQuery("from Customer where cname = ?") .setString(0, "小明").uniqueResult(); System.out.println(customer); 2.7 参数绑定 // 1.使用?号方式绑定 /*Query query = session.createQuery("from Customer where cname = ?"); query.setString(0, "小沈"); List<Customer> list = query.list(); System.out.println(list);*/ /*Query query = session.createQuery("from Customer where cname = ? and cid =?"); query.setString(0, "小沈"); query.setInteger(1,3); List<Customer> list = query.list(); System.out.println(list);*/ // 2.使用名称的方式绑定 Query query = session.createQuery("from Customer where cname=:name and cid=:id"); query.setString("name", "小沈"); query.setInteger("id", 3); List<Customer> list = query.list(); System.out.println(list); // 3.绑定实体 List<Order> list = session .createQuery("from Order o where o.customer = ?") .setEntity(0, customer).list(); for (Order order : list) { System.out.println(order); } 2.8 投影操作 // 查询客户的名称: List<Object> list = session.createQuery( "select c.cname from Customer c").list(); System.out.println(list); List<Object[]> list = session.createQuery( "select c.cid,c.cname from Customer c").list(); for (Object[] objects : list){ System.out.println(Arrays.toString(objects)); } List<Customer> list = session.createQuery( "select new Customer(cname) from Customer").list(); System.out.println(list); 2.9 模糊查询 Query query = session.createQuery(" from Customer where cname like ?"); query.setParameter(0, "小%"); List<Customer> list = query.list(); System.out.println(list); 2.10 SQL多表查询

连接:

交叉连接:

select * from A,B;

内连接:查询的是两个表的交集!

select * from A inner join B on A.字段 = B.字段;

隐式内连接:

select * from A,B where A.字段 = B.字段;

外连接:

左外连接:

select * from A left outer join B on A.字段 = B.字段;

右外连接:

select * from A right outer join B on A.字段 = B.字段;

2.11 HQL多表的查询

连接:

交叉连接:

内连接:

隐式内连接:

迫切内连接:

左外连接:

迫切左外连接:

右外连接:

HQL的内连接和迫切内连接区别:

内连接查询 :将数据封装一个List中.

迫切内连接 :将数据封装一个List中.但是迫切内连接,得到会有重复记录 ,需要使用distinct排重.

三、QBC 3.1 简介 3.2 查询所有记录 List<Customer> list =session.createCriteria(Customer.class).list(); for (Customer customer : list) { System.out.println(customer); } 3.3 排序 List<Customer> list = session.createCriteria(Customer.class) .addOrder(org.hibernate.criterion.Order.desc("id")).list(); for (Customer customer : list) { System.out.println(customer); } 3.4分页 Criteria criteria = session.createCriteria(Order.class); criteria.setFirstResult(10); criteria.setMaxResults(10); List<Order> list = criteria.list(); for (Order order : list) { System.out.println(order); } 3.5获取单个对象 Customer customer = (Customer) session.createCriteria(Customer.class) .add(Restrictions.eq("cname", "小明")).uniqueResult(); System.out.println(customer); 3.6 带参数的查询 /* List<Customer> list = session.createCriteria(Customer.class) .add(Restrictions.eq("cname", "小明")).list(); System.out.println(list); */ List<Customer> list = session.createCriteria(Customer.class) .add(Restrictions.eq("cname", "小明")) .add(Restrictions.eq("cid", 2)).list(); System.out.println(list); 3.7 模糊查询 Criteria criteria = session.createCriteria(Customer.class); criteria.add(Restrictions.like("cname", "大%")); List<Customer> list = criteria.list(); System.out.println(list); 四、SQL 4.1 简介 4.2 SQL语句查询所有记录 List<Object[]> list = session.createSQLQuery("select * from customer").list(); for (Object[] objects : list) { System.out.println(Arrays.toString(objects)); } List<Customer> list = session.createSQLQuery("select * from customer").addEntity(Customer.class).list(); for (Customer customer : list) { System.out.println(customer); }

【Hibernate】检索方式

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