HQL语句学习

<span style="font-size:18px;"><strong>package com.hsp.view;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.Transaction;
import com.hsp.util.HibernateUtil;
import com.sina.domain.Studcourse;
import com.sina.domain.Student;
public class TestMain {
	public static void main(String[] args) {	
		//这我们举例说明hql使用
		Session session=null;
		Transaction tx=null;
		try {
			session=HibernateUtil.getCurrentSession();
			tx=session.beginTransaction();
			//比如，显示所有学生的性别和年龄.
			Query query=session.createQuery("from Student where sdept=? and sage>?");
			
			query.setString(0, "计算机系");
			query.setString(1, "2");
			List <Student> list=query.list();
			for(int i=0;i<list.size();i++){
				Student s= list.get(i);
				System.out.println(s.getSname()+" "+s.getSage());
			}
			
			//计算年龄在20~22之间的学生
			
		/*	List list=session.createQuery("select distinct sage,ssex,sname from Student where sage between 20 and 22").list();
			for(int i=0;i<list.size();i++){
				Object []  objs=(Object[]) list.get(i);
				System.out.println(objs[0].toString()+" "+objs[1].toString()+objs[2].toString());
			}*/
			
			//查询计算机系和外语系的学生信息
			
			/*List<Student> list=session.createQuery("from Student where sdept not in ('计算机系','外语系')").list();
			//取出1. for 增强
			for(Student s:list){
				System.out.println(s.getSname()+" "+s.getSaddress()+" "+s.getSdept());
			}
			*/
			//显示各个系的学生的平均年龄
		/*	List<Object[]> list=session.createQuery("select avg(sage),sdept from  Student group by sdept").list();
			//取出1. for 增强
			for(Object[] obj:list){
				System.out.println(obj[0].toString()+" "+obj[1].toString());
			}*/
			
			//having的使用
			//1.对分组查询后的结果，进行筛选:比如请显示人数大于3的系名称
			//a. 查询各个系分别有多少学生.
			
	/*		List<Object[]> list=session.createQuery("select count(*) as c1,sdept from  Student group by sdept having count(*)>3").list();
			//取出1. for 增强
			for(Object[] obj:list){
				System.out.println(obj[0].toString()+" "+obj[1].toString());
			}*/
			
			//2查询女生少于200人的系
			//a.查询各个系的女生有多个个
		/*	List<Object[]> list=session.
			createQuery("select count(*) as c1,sdept from  Student where ssex='F' group by sdept").list();
			//取出1. for 增强
			for(Object[] obj:list){
				System.out.println(obj[0].toString()+" "+obj[1].toString());
			}*/
			
			//		1.查询计算机系共多少人?->如果我们返回的是一列数据
			//这时我们的取法是直接取出list->object 而不是 list->Object[]
	/*		List<Object[]> list=session.
			createQuery("select sage from  Student where sdept='计算机系'").list();
			//取出1. for 增强
			for(Object obj:list){
				System.out.println(obj.toString());
			}*/
//					2.查询总学分是多少?
/*			List<Object[]> list=session.
			createQuery("select sum(grade) from Studcourse").list();
			//取出1. for 增强
			for(Object obj:list){
				System.out.println(obj.toString());
			}*/
//					3.查询选修11号课程的最高分和最低分.
/*			List<Object[]> list=session.
			createQuery("select 11,max(grade),min(grade) from Studcourse where course.cid=11").list();
			//取出1. for 增强
			for(Object[] obj:list){
				System.out.println(obj[0].toString()+" max="+obj[1].toString()+" min="+obj[2].toString());
			}*/
			//4.显示各科考试不及格学生的名字(Student-student)，科目(Course-course)和分数(Studcourse-studcourse)
			
		/*	List<Object[]> list=session.
			createQuery("select student.sname,course.cname,grade from Studcourse where grade>=60").list();
			//取出1. for 增强
			for(Object[] obj:list){
				System.out.println(obj[0].toString()+" "+obj[1].toString()+" "+obj[2].toString());
			}*/
			
			//计算各个科目不及格的学生数量.(学生练习!)
			
			/*List<Object[]> list=session.
			createQuery("select count(*),student.sdept from Studcourse where grade<60 group by student.sdept").list();
			//取出1. for 增强
			for(Object[] obj:list){
				System.out.println(obj[0].toString()+" "+obj[1].toString());
			}*/
			
			//请按照学生的年龄从小->大，取出第3到第5个学生
		/*	List<Student> list=session.createQuery
			("from Student  order by sage").setFirstResult(2)
			.setMaxResults(3).list();
			for(Student s: list){
				System.out.println(s.getSname()+" "+s.getSage());
			}*/
			
			
			
			tx.commit();
			
			
		} catch (Exception e) {
			e.printStackTrace();
			if(tx!=null){
				tx.rollback();
			}
			throw new RuntimeException(e.getMessage());
			// TODO: handle exception
		}finally{
			if(session!=null&&session.isOpen()){
				session.close();
			}
			
		}
		
	}
	
	//分页函数
	private static void showResultByPage(int pageSize){
		//设置分页的变量
		int pageNow=1;
		int pageCount=1;//计算
		int rowCount=1;//这个需要查询
		
		Session session=null;
		Transaction tx=null;
		try {
			session=HibernateUtil.getCurrentSession();
			tx=session.beginTransaction();
			
			//查询出rowcount
			rowCount=Integer.parseInt(session.createQuery("select count(*) from Student").uniqueResult().toString());
			pageCount=(rowCount-1)/pageSize+1;
			
			//现在我们可以循环的显示每页的信息
			for(int i=1;i<=pageCount;i++){
				System.out.println("************第"+i+"页************");
				List<Student> list=session.createQuery("from Student").setFirstResult((i-1)*pageSize)
				.setMaxResults(pageSize).list();
				for(Student s: list){
					System.out.println(s.getSname()+" "+s.getSdept());
				}
				
			}
			
			tx.commit();
			
		}catch(Exception e){
			e.printStackTrace();
			if(tx!=null){
				tx.rollback();
			}
			throw new RuntimeException(e.getMessage());
		}finally{
			if(session!=null&&session.isOpen()){
				session.close();
			}
		}
		
	}
	

	private static void query2() {
		//这我们举例说明hql使用
		Session session=null;
		Transaction tx=null;
		try {
			session=HibernateUtil.getCurrentSession();
			tx=session.beginTransaction();
			//hql
			//1.检索的学生名字和所在系
			//原则: 在讲解jdbc我们曾说过， 要查询什么字段就查询什么字段，不要select * from 表
			//但是在hibernate ,我们其实可以不遵循这个规则,建议我们把整个对象的属性都查询
			//这里我们还是要讲解如何取出部分属性
			
			
			List list=session.createQuery("select sname,sdept from Student").list();
			
			for(int i=0;i<list.size();i++){
				Object []  objs=(Object[]) list.get(i);
				System.out.println(objs[0].toString()+" "+objs[1].toString());
			}
			System.out.println("****************");
			//如果使用iterator
			Iterator it=list.iterator();
			while(it.hasNext()){
				Object [] objs=(Object[]) it.next();
				System.out.println(objs[0].toString()+" "+objs[1].toString());
			}
			
			tx.commit();
			
			
			
		} catch (Exception e) {
			e.printStackTrace();
			if(tx!=null){
				tx.rollback();
			}
			throw new RuntimeException(e.getMessage());
			// TODO: handle exception
		}finally{
			if(session!=null&&session.isOpen()){
				session.close();
			}
			
		}
	}

	public static void query1() {
		//这我们举例说明hql使用
		Session session=null;
		Transaction tx=null;
		try {
			session=HibernateUtil.getCurrentSession();
			tx=session.beginTransaction();
			//hql
			//1.检索所有的学生
			List<Student> list=session.createQuery("from Student").list();
			//取出1. for 增强
			for(Student s:list){
				System.out.println(s.getSname()+" "+s.getSaddress());
			}
			System.out.println("*****************");
			//2. 使用iterator
			Iterator<Student> iterator=list.iterator();
			while(iterator.hasNext()){
				Student s=iterator.next();
				System.out.println(s.getSname()+" "+s.getSage());
			}
			
			tx.commit();
			
		} catch (Exception e) {
			e.printStackTrace();
			if(tx!=null){
				tx.rollback();
			}
			throw new RuntimeException(e.getMessage());
			// TODO: handle exception
		}finally{
			if(session!=null&&session.isOpen()){
				session.close();
			}
			
		}
	}
}
</strong></span>