hibernate教程--检索方式详解（hql，sql，QBC）

1.1 Hibernate的检索方式

1.1.1 Hibernate的检索方式:

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”);

1.1.2 HQL:

HQL:Hibernate Query Language:

* 特点:

* 面向对象的查询:

* 支持方法链编程:

* 使用:

1.查询所有记录:

List<Customer> list = session.createQuery("from Customer").list();

for (Customer customer : list) {

System.out.println(customer);

}

2.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);

3.排序:

List<Customer> list = session.createQuery(

"from Customer c order by c.id desc").list();

for (Customer customer : list) {

System.out.println(customer);

}

4.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);

}

5.单个对象查询:

Customer customer = (Customer) session

.createQuery("from Customer where cname = ?")

.setString(0, "小明").uniqueResult();

System.out.println(customer);

6.参数绑定:

// 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);

}

7.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);

8.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);

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;

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<Object[]>中.

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

1.1.3 QBC:

1.查询所有记录:

List<Customer> list = session.createCriteria(Customer.class).list();

for (Customer customer : list) {

System.out.println(customer);

}

2.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.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);

}

4.获取单个对象:

Customer customer = (Customer) session.createCriteria(Customer.class)

.add(Restrictions.eq("cname", "小明")).uniqueResult();

System.out.println(customer);

5.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);

6.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);

1.1.4 SQL:

1.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);

}