标签：

一、Hibernate的查询方式：OID查询 1、OID检索：Hibernate根据对象的OID（主键）进行检索

1-1、使用get方法

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

1-2、使用load方法

Customer customer = session.load(Customer.class,1L);

3、对象导航检索：Hibernate根据一个已经查询到的对象，获得其关联的对象的一种查询方式。

Customer customer = session.get(Customer.class,1L); Set<LinkMan> linkManSet = customer.getLinkMans();

4-1、HQL查询

Hibernate Query Language，Hibernate的查询语言，是一种面向对象的方式的查询语言，语法类似SQL。通过session.createQuery()，用于接收一个HQL进行查询方式。

package com.turtle.test; import java.util.Arrays; import java.util.List; import com.turtle.dao.Customer; import com.turtle.dao.LinkMan; import com.turtle.utils.HibernateUtils; import org.hibernate.Query; import org.hibernate.Session; import org.hibernate.Transaction; import org.junit.Test; /** * HQL的查询方式的测试类 * * @author jt * */ public class Hibernater_01 { @Test /** * 初始化数据 */ public void demo1() { Session session = HibernateUtils.getCurrentSession(); Transaction tx = session.beginTransaction(); // 创建一个客户 Customer customer = new Customer(); customer.setCust_name("李向文"); for (int i = 1; i <= 10; i++) { LinkMan linkMan = new LinkMan(); linkMan.setLkm_name("王东" + i); linkMan.setCustomer(customer); customer.getLinkMans().add(linkMan); session.save(linkMan); } session.save(customer); tx.commit(); } @Test /** * HQL的简单查询 */ public void demo2() { Session session = HibernateUtils.getCurrentSession(); Transaction tx = session.beginTransaction(); // 简单的查询 Query query = session.createQuery("from Customer"); List<Customer> list = query.list(); // sql中支持*号的写法：select * from cst_customer; 但是在HQL中不支持*号的写法。 /* * Query query = session.createQuery("select * from Customer");// 报错 * List<Customer> list = query.list(); */ for (Customer customer : list) { System.out.println(customer); } tx.commit(); } @Test /** * 别名查询 */ public void demo3() { Session session = HibernateUtils.getCurrentSession(); Transaction tx = session.beginTransaction(); // 别名的查询 /* * Query query = session.createQuery("from Customer c"); List<Customer> * list = query.list(); */ Query query = session.createQuery("select c from Customer c"); List<Customer> list = query.list(); for (Customer customer : list) { System.out.println(customer); } tx.commit(); } @Test /** * 排序查询 */ public void demo4() { Session session = HibernateUtils.getCurrentSession(); Transaction tx = session.beginTransaction(); // 排序的查询 // 默认情况 // List<Customer> list = session.createQuery("from Customer order by // cust_id").list(); // 设置降序排序 升序使用asc 降序使用desc List<Customer> list = session.createQuery("from Customer order by cust_id desc").list(); for (Customer customer : list) { System.out.println(customer); } tx.commit(); } @Test /** * 条件查询 */ public void demo5() { Session session = HibernateUtils.getCurrentSession(); Transaction tx = session.beginTransaction(); // 条件的查询 // 一、按位置绑定：根据参数的位置进行绑定。 // 一个条件 /* * Query query = session.createQuery("from Customer where cust_name = ?"); * query.setParameter(0, "李兵"); * List<Customer> list = query.list(); */ // 多个条件 /* * Query query = session.createQuery( * "from Customer where cust_source = ? and cust_name like ?"); * query.setParameter(0, "小广告"); * query.setParameter(1, "李%"); * List<Customer> list = query.list(); */ // 二、按名称绑定 Query query = session.createQuery("from Customer where cust_source = :aaa and cust_name like :bbb"); // 设置参数: query.setParameter("aaa", "朋友推荐"); query.setParameter("bbb", "李%"); List<Customer> list = query.list(); for (Customer customer : list) { System.out.println(customer); } tx.commit(); } @Test /** * 投影查询 */ public void demo6() { Session session = HibernateUtils.getCurrentSession(); Transaction tx = session.beginTransaction(); // 投影查询 // 单个属性 /* * List<Object> list = session.createQuery("select c.cust_name from Customer c").list(); * for (Object object :list) { * System.out.println(object); * } */ // 多个属性: /* * List<Object[]> list = session.createQuery( * "select c.cust_name,c.cust_source from Customer c").list(); for * (Object[] objects : list) { * System.out.println(Arrays.toString(objects)); } */ // 查询多个属性，但是我想封装到对象中。 List<Customer> list = session.createQuery("select new Customer(cust_name,cust_source) from Customer").list(); for (Customer customer : list) { System.out.println(customer); } tx.commit(); } @Test /** * 分页查询 */ public void demo7() { Session session = HibernateUtils.getCurrentSession(); Transaction tx = session.beginTransaction(); // 分页查询 Query query = session.createQuery("from LinkMan"); query.setFirstResult(20); query.setMaxResults(10); List<LinkMan> list = query.list(); for (LinkMan linkMan : list) { System.out.println(linkMan); } tx.commit(); } @Test /** * 分组统计查询 */ public void demo8() { Session session = HibernateUtils.getCurrentSession(); Transaction tx = session.beginTransaction(); // 聚合函数的使用：count(),max(),min(),avg(),sum() Object object = session.createQuery("select count(*) from Customer").uniqueResult(); System.out.println(object); // 分组统计： List<Object[]> list = session.createQuery("select cust_source,count(*) from Customer group by cust_source") .list(); for (Object[] objects : list) { System.out.println(Arrays.toString(objects)); } tx.commit(); } @Test /** * HQL的多表查询 */ public void demo9() { Session session = HibernateUtils.getCurrentSession(); Transaction tx = session.beginTransaction(); // SQL:SELECT * FROM cst_customer c INNER JOIN cst_linkman l ON // c.cust_id = l.lkm_cust_id; // HQL:内连接 from Customer c inner join c.linkMans /* * List<Object[]> list = session.createQuery("from Customer c inner join c.linkMans").list(); * for (Object[] objects : list) { * System.out.println(Arrays.toString(objects)); * } */ // HQL:迫切内连接 其实就在普通的内连接inner join后添加一个关键字fetch. from Customer c inner // join fetch c.linkMans List<Customer> list = session.createQuery("select distinct c from Customer c inner join fetch c.linkMans") .list();// 通知hibernate，将另一个对象的数据封装到该对象中 for (Customer customer : list) { System.out.println(customer); } tx.commit(); } }

4-2、 HQL的多表查询

  SQL的多表查询

  连接查询

  交叉连接：笛卡尔积

select * from A,B;

  内连接    :inner join (inner 可以省略)

  隐式内连接：

select * from A,B where A.id = B.aid;

  显示内连接：

select * from A inner join B on A.id = B.aid;

  外连接    :

  左外连接:left outer join(outer 可以省略)

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

  右外连接:right outer join(outer 可以省略)

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

  子查询

 

 HQL的多表查询

  连接查询

  交叉连接

  内连接

  显示内连接

  隐式内连接

  迫切内连接

  外连接

  左外连接

  右外连接

  迫切左外连接

5、QBC查询：Query By Criteria，条件查询。是一种更加面向对象化的查询的方式。