HQL常用查询

1.全选

      org.hibernate.Query query = session.createQuery("from Student");

      java.util.Iterator iterator = query.list().iterator();

      tx.commit();

      while (iterator.hasNext()){

             Student student = (Student)iterator.next();

             System.out.println("--------------------------------");

             System.out.println(student.getStudentId());

             System.out.println(student.getName());    

      }

       

注意:查询语句中的不是表格名而是对象名，所以必须大写

 

2.选择

 （1）固定参数

      org.hibernate.Query query = session.createQuery("from Student s where s.name='朱红'");

      java.util.Iterator iterator = query.list().iterator();

      tx.commit();

      while (iterator.hasNext()){

             Student student = (Student)iterator.next();

             System.out.println("--------------------------------");

             System.out.println(student.getStudentId());

             System.out.println(student.getName());    

}

 （2）位置参数

      org.hibernate.Query query = session.createQuery("from Student s where s.id=?");

      query.setParameter(0,"001");

      java.util.Iterator iterator = query.list().iterator();

      tx.commit();

      while (iterator.hasNext()){

             Student student = (Student)iterator.next();

             System.out.println("--------------------------------");

             System.out.println(student.getStudentId());

             System.out.println(student.getName());    

      }

 （3）命名参数

      org.hibernate.Query query = session.createQuery("from Student s where s.id=:student_id");

      query.setParameter("student_id","007");

      java.util.Iterator iterator = query.list().iterator();

      tx.commit();

3．投影

  org.hibernate.Query query = session.createQuery("select s.studentId,s.name from Student s ");

      java.util.Iterator iterator = query.list().iterator();

     

      while (iterator.hasNext()){

             Object[] row = (Object[])iterator.next();

             System.out.println("--------------------------------");

             System.out.println((String)row[0]);

}

 

//执行的过程中存在奇怪的问题，只查询一个表，只查询一列时候才出现的错误，只要选择两列以上就没问题了

//查询两个以上表格时，也存在该问题

 

4．连接

根据子类查找父类信息

org.hibernate.Query query = session.createQuery("select c.id,c.className from Zlass c inner join c.students s where s.studentId='001'");

java.util.Iterator iterator = query.list().iterator();

     

while (iterator.hasNext()){

             Object[] row = (Object[])iterator.next();

             System.out.println("--------------------------------");

             System.out.println((String)row[0]+(String)row[1]);

}

 

//根据父类查找子类

org.hibernate.Query query = session.createQuery("from Zlass c where c.id='971002'");

      java.util.Iterator iterator = query.list().iterator();

     

      while (iterator.hasNext()){

          Zlass row = (Zlass)iterator.next();

             java.util.Iterator i = row.getStudents().iterator();

             while(i.hasNext()){

                 Student s = (Student)i.next();

            System.out.println("--------------------------------");

            System.out.println(s.getStudentId()+" "+s.getName());

        }

      }

 //根据父类查找子类2，使用elements

 org.hibernate.Query query = session.createQuery("select elements(c.students) from Zlass c where c.id='971002'");

      java.util.Iterator iterator = query.list().iterator();

     

      while (iterator.hasNext()){

                 Student s = (Student)iterator.next();

            System.out.println("--------------------------------");

            System.out.println(s.getStudentId()+" "+s.getName());

      }