Hibernate学习-11-几种查询详解

  //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);

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

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
     //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());