/**
     * @param f
     * @throws TODO
     *             图书续借
     */
    public boolean reborrow(Connection con, String id) {        this.bookid = id;
        String tableName = "message";//数据库用户表信息表        boolean v = false;
        int result = 0;
        Statement stmt = null;
        Date dNow = new Date();        SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
        String today = formatter.format(dNow);
        System.out.print("\n"+bookid+"\n" + today + "\n");
        try {
            stmt = con.createStatement();            String isCorrect = "update message"
                    + " set reborrowday = '" + today
                    + "',returnday = '" + today + "' where bookid = '" + bookid
                    + "'";            result = stmt.executeUpdate(isCorrect);            System.out.print(":" + result + "\n");
 
        } catch (Exception e) {
            System.out.println("error1 is  " + e);
        } finally {
            try {
                stmt.close();
                con.close();
            } catch (SQLException ex) {
                System.out.println("error2 is  " + ex);
            }
        }        return v;    }总是Unknown column reborrowday in 'field list'
我表里有reborrowday的字段,怎么会未知呢?