Hibernate学习-11-几种查询详解

来源：互联网发布：php二进制转换字符串编辑：程序博客网时间：2024/04/30 06:06

1）Get/load主键查询

  //1)主键查询

  // Dept dept = (Dept)session.load(Dept.class,1);

  // Dept dept = (Dept)session.get(Dept.class,1); 
     
     System.out.println(dept);

结果

Hibernate:     select        dept0_.deptId as deptId0_0_,        dept0_.deptName as deptName0_0_     from        t_dept dept0_     where        dept0_.deptId=?com.cx.hqlQuery.Dept@302552ec

2) 对象导航查询

        //2)对象导航查询        Dept dept = (Dept)session.get(Dept.class,1);        System.out.println(dept.getEmployees());

结果

Hibernate:     select        dept0_.deptId as deptId0_0_,        dept0_.deptName as deptName0_0_     from        t_dept dept0_     where        dept0_.deptId=?Hibernate:     select        employees0_.dept_id as dept4_0_1_,        employees0_.empId as empId1_,        employees0_.empId as empId1_0_,        employees0_.empName as empName1_0_,        employees0_.salary as salary1_0_,        employees0_.dept_id as dept4_1_0_     from        t_employee employees0_     where        employees0_.dept_id=?[com.cx.hqlQuery.Employee@7bedc48a, com.cx.hqlQuery.Employee@38afe297]

3)HQL查询

使用hql查询的时候，映射文件auto-import="true"要设置为true,如果是false，在写hql的时候，要指定类的全名。

     //3)HQL查询     //a查询全部列     Query q = session.createQuery("from Employee");     System.out.println(q.list());
     //b查询指定列
     Query q = session.createQuery("select d.deptId , d.deptName from Dept d");
     System.out.println(q.list());
     //c查询指定列，自动封装为对象(必须提供有参数的构造器)   
     Query q = session.createQuery("select new Dept(d.deptId,d.deptName) from Dept d");     System.out.println(((Dept)q.list().get(0)).getDeptName());     //d 条件查询     //条件查询-占位符     Query q = session.createQuery("from Dept d where deptName = ?");   
     // q.setString(0,"综合部");     q.setParameter(0,"综合部");     System.out.println(q.list());     //条件查询，命名参数     Query q = session.createQuery("from Dept d where deptId=:myId or deptName=:name");     q.setParameter("myId",1);     q.setParameter("name","综合部");     System.out.println(q.list());        //范围     Query q = session.createQuery("from Dept d where deptId between ? and ?");     q.setParameter(0,1);     q.setParameter(1,6);     System.out.println(q.list());

     //模糊查询
     Query  q = session.createQuery("from Dept d where deptName like ?");
     q.setString(0,"%部%");
     System.out.println(q.list());

     //e.聚合函数统计     Query q = session.createQuery("select count (*) from Dept");     Long num = (Long)q.uniqueResult();     System.out.println(num);

     //分组查询，统计每个部门的人数     Query q = session.createQuery("select e.dept , count(*) from Employee e group by e.dept");     System.out.println(q.list());

连接查询

    @Test    public void testJoin(){        Session session = sf.openSession();        session.beginTransaction();        //内连接 映射已经配置好了关系，关联的时候，直接写对象的属性即可        Query q = session.createQuery("from Dept d inner join d.employees");      //  System.out.println(q.list());        List<Object []> list= q.list();        for (int i = 0 ; i < list.size() ; i++) {            Object[] obj = list.get(i);            Employee employee = (Employee) obj[1];            Dept dept = (Dept) obj[0];            System.out.println(employee.getEmpName() + "-" + dept.getDeptName());        }        //2)左外连接//        Query q = session.createQuery("from Dept d left join d.employees");//        System.out.println(q.list());//        //3)右外连接//        Query q = session.createQuery("from Employee e right join e.dept");//        System.out.println(q.list());        session.getTransaction().commit();        session.close();     }

迫切连接查询

    // g. 连接查询 - 迫切连接    @Test    public void fetch() {                Session session = sf.openSession();        session.beginTransaction();                //1) 迫切内连接    【使用fetch, 会把右表的数据，填充到左表对象中！】//        Query q = session.createQuery("from Dept d inner join fetch d.emps");//        q.list();                //2) 迫切左外连接        Query q = session.createQuery("from Dept d left join fetch d.emps");        q.list();                session.getTransaction().commit();        session.close();    }

4) Criteria 查询

    @Test    public void criteria() {                Session session = sf.openSession();        session.beginTransaction();                Criteria criteria = session.createCriteria(Employee.class);        // 构建条件        criteria.add(Restrictions.eq("empId", 12));//        criteria.add(Restrictions.idEq(12));  // 主键查询                System.out.println(criteria.list());                        session.getTransaction().commit();        session.close();    }

5)本地sql查询

    // 不能跨数据库平台： 如果该了数据库，sql语句有肯能要改。    @Test    public void sql() {                Session session = sf.openSession();        session.beginTransaction();                SQLQuery q = session.createSQLQuery("SELECT * FROM t_Dept limit 5;")            .addEntity(Dept.class);  // 也可以自动封装        System.out.println(q.list());                session.getTransaction().commit();        session.close();    }

0 0