public int delete(int id){
		String sql = "delete from student where id = ?";
		conn = DbUtil.getConnection();
		int affectRows = 0;
		try {
			pstmt = conn.prepareStatement(sql);
			pstmt.setInt(1, id);
			affectRows = pstmt.executeUpdate();
		} catch (SQLException e) {
			e.printStackTrace();
		} finally{
			DbUtil.close(rs, pstmt, conn);
		}
		return affectRows;
	}