public ResultSet executeUpdateQuery(String sql) {
		if (stmt != null) {
			try {
				stmt.close();
			} catch (SQLException e) {
				e.printStackTrace();
				return null;
			}
		}
		try {
			stmt = conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,
					ResultSet.CONCUR_UPDATABLE);
		} catch (SQLException e) {
			e.printStackTrace();
			return null;
		} // Statement󣬿ɻعɸ
		try {
			return stmt.executeQuery(sql);
		} catch (SQLException e) {
			e.printStackTrace();
			return null;
		}
	}