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Day04

目录标题

1. 对象导航查询

查询某个客户里面所有联系人过程，使用对象导航实现。

代码

// 根据cid=1客户，再查询这个客户里面所有联系人Customer customer = session.get(Customer.class, 1);// 直接得到客户里面联系人的set集合Set
   
     linkman = customer.getSetLinkMan();// 发送语句System.out.println(linkman.size());
   

2. OID查询

根据id查询记录

代码

// 根据cid=1客户，再查询这个客户里面所有联系人Customer customer = session.get(Customer.class, 1);

3. HQL查询

hibernate query language，用于对实体类进行查询操作。

HQL常用语句

查询所有客户

// 创建query对象Query query = session.createQuery("from Customer");// 调用方法得到结果List
   
     list = query.list();// 遍历结果for (Customer customer : list) {    System.out.println(customer.getCid() + "::" + customer.getCustName());}
   

条件查询

// 创建query对象Query query = session.createQuery("from Customer c where c.cid=? and c.custName=?");// 设置参数值query.setParameter(0, 1); // cid=1query.setParameter(1, "百度"); // custName=百度// 获取结果List
   
     list = query.list();for (Customer customer : list) {    System.out.println(customer.getCid() + "::" + customer.getCustName());}
   

模糊查询

// 创建query对象Query query = session.createQuery("from Customer c where c.custName like ?");// 设置参数值query.setParameter(0, "%百%"); // 模糊查询百度// 获取结果List
   
     list = query.list();for (Customer customer : list) {    System.out.println(customer.getCid() + "::" + customer.getCustName());}
   

排序查询

// 创建query对象Query query = session.createQuery("from Customer order by cid desc");// 获取结果List
   
     list = query.list();for (Customer customer : list) {    System.out.println(customer.getCid() + "::" + customer.getCustName());}
   

分页查询

// 创建query对象Query query = session.createQuery("from Customer");// 设置分页参数query.setFirstResult(0); // 起始位置query.setMaxResults(3); // 每页显示的记录数// 获取结果List
   
     list = query.list();for (Customer customer : list) {    System.out.println(customer.getCid() + "::" + customer.getCustName());}
   

投影查询

// 创建query对象Query query = session.createQuery("select custName from Customer");// 获取结果List

聚集函数

// 查询客户总数Query query = session.createQuery("select count(*) from Customer");Object obj = query.uniqueResult();Long lobj = (Long) obj;int count = lobj.intValue();System.out.println(count);

4. QBC查询

使用Criteria对象实现查询

查询所有

// 创建Criteria对象Criteria criteria = session.createCriteria(Customer.class);// 获取结果List
   
     list = criteria.list();for (Customer customer : list) {    System.out.println(customer.getCid() + "::" + customer.getCustName());}
   

条件查询

// 创建Criteria对象Criteria criteria = session.createCriteria(Customer.class);// 添加条件criteria.add(Restrictions.eq("cid", 1));criteria.add(Restrictions.like("custName", "%百%"));// 获取结果List
   
     list = criteria.list();for (Customer customer : list) {    System.out.println(customer.getCid() + "::" + customer.getCustName());}
   

排序查询

// 创建Criteria对象Criteria criteria = session.createCriteria(Customer.class);// 设置排序规则criteria.addOrder(Order.desc("cid"));// 获取结果List
   
     list = criteria.list();for (Customer customer : list) {    System.out.println(customer.getCid() + "::" + customer.getCustName());}
   

分页查询

// 创建Criteria对象Criteria criteria = session.createCriteria(Customer.class);// 设置分页参数criteria.setFirstResult(0);criteria.setMaxResults(3);// 获取结果List
   
     list = criteria.list();for (Customer customer : list) {    System.out.println(customer.getCid() + "::" + customer.getCustName());}
   

统计查询

// 创建Criteria对象Criteria criteria = session.createCriteria(Customer.class);// 设置投影操作criteria.setProjection(Projections.rowCount());// 获取结果Object obj = criteria.uniqueResult();Long lobj = (Long) obj;int count = lobj.intValue();System.out.println(count);

离线查询

// 创建DetachedCriteria对象DetachedCriteria detachedCriteria = DetachedCriteria.forClass(Customer.class);// 获取执行的Criteria对象Criteria criteria = detachedCriteria.getExecutableCriteria(session);// 获取结果List
   
     list = criteria.list();for (Customer customer : list) {    System.out.println(customer.getCid() + "::" + customer.getCustName());}
   

HQL多表查询

Mysql多表查询

HQL多表查询

HQL内连接

// 创建query对象Query query = session.createQuery("from Customer c inner join c.setLinkMan");// 获取结果List list = query.list();

迫切内连接

// 创建query对象Query query = session.createQuery("from Customer c inner join fetch c.setLinkMan");// 获取结果List list = query.list();

HQL左外连接

// 创建query对象Query query = session.createQuery("from Customer c left outer join c.setLinkMan");// 获取结果List list = query.list();

迫切左外连接

// 创建query对象Query query = session.createQuery("from Customer c left outer join fetch c.setLinkMan");// 获取结果List list = query.list();

Hibernate检索策略

延迟查询

// 延迟查询客户Customer customer = session.load(Customer.class, 2);// 获取客户信息System.out.println(customer.getCid());System.out.println(customer.getCustName());

关联级别延迟

// 根据cid=1客户，再查询这个客户里面所有联系人Customer customer = session.get(Customer.class, 1);// 获取客户的联系人Set
   
     linkman = customer.getSetLinkMan();// 输出联系人数量System.out.println(linkman.size());
   

批量抓取

// 查询所有客户Criteria criteria = session.createCriteria(Customer.class);List
   
     list = criteria.list();// 获取每个客户的联系人for (Customer customer : list) {    Set
    
      linkman = customer.getSetLinkMan();    for (LinkMan linkMan : linkman) {        System.out.println(linkMan.getLkm_id() + "::" + linkMan.getLkm_name());    }}
    
   

批量设置