/**
	 * 分页方法，根据指定页列出学生的信息
            * 根据tid，当tid为零，显示所有学生信息，其他均为老师的id
	 * @param students
	 * @param pageSize 页的大小
	 * @param pageNo   当前页
	 * @param tid      老师的ID号
	 * @return total   总记录数
	 * @throws Exception
	 */
	public int listStudent(List<Student> students,int pageSize,int pageNo,int tid)throws Exception{
		int total=0;
		String sql1="select top "+pageSize+" s.susername,s.sname,t.tname,s.ssex,s.stelephone,s.semail "
				  +" from student s left join teacher t on(s.tid=t.id) where "
		           +"(s.id not in(select top "+(pageNo-1)*pageSize+" s.id from student s order by s.id))order by s.id";
		String sql2="select top "+pageSize+" s.susername,s.sname,t.tname,s.ssex,s.stelephone,s.semail "
		  +" from student s left join teacher t on(s.tid=t.id) where s.tid="+tid
         +" and (s.id not in(select top "+(pageNo-1)*pageSize+" s.id from student s order by s.id)) order by s.id";
		conn=DB.getConnection();
		Statement stmtCount=null;
		stmtCount=DB.getStatement(conn);
		if(tid==0){
			rs=stmtCount.executeQuery("select count(*) from student");
		}else{
			rs=stmtCount.executeQuery("select count(*) from student s where s.tid="+tid);
		}
		
		while(rs.next()){
			total=rs.getInt(1);
		}
		rs=null;
		stmt=DB.getStatement(conn);
		if(tid==0){
			rs=stmt.executeQuery(sql1);
		}else{
			students.clear();
			rs=stmt.executeQuery(sql2);
		}
		while(rs.next()){
			Teacher t=new  Teacher();
			t.setName(rs.getString("tname"));
			
			Student s=new Student();
			s.setUsername(rs.getString("susername"));
			s.setName(rs.getString("sname"));
			s.setSex(rs.getString("ssex"));
			s.setTelephone(rs.getString("stelephone"));
			s.setEmail(rs.getString("semail"));
			s.setTeacher(t);
			
			students.add(s);
		}
		stmtCount.close();
		DB.close(rs, stmt, conn);
		return total;
	}