public String selectPower(String usName){
		String power=null;
		connectionDB();
		String sql="select power from US where userName=?";
		try {
			ps=conn.prepareStatement(sql);
			ps.setString(1, usName);
			rs=ps.executeQuery();
			while(rs.next()){
				power=new String();
				power=rs.getString("power");	
			}
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally{
			closeDB();
		}
		return power;
	}