c#保存datagridview中的数据时报错 “动态SQL生成失败。找不到关键信息”

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using Oracle.ManagedDataAccess.Client;
using Oracle.ManagedDataAccess.Types;
 
namespace 订单系统
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private DataSet ds;
        private OracleDataAdapter oda;
        private OracleConnection con;
        private OracleCommand cmd;
 
        private void Form1_Load(object sender, EventArgs e)
        {
            try
            {
                string conString = "User Id=dingzi; password=dingzi;" + "Data Source=localhost:1521/orcl; Pooling=false;";
                con = new OracleConnection();
                con.ConnectionString = conString;
                con.Open();
                cmd = con.CreateCommand();
                cmd.CommandText = "select * from stock order by 订货日期 desc";
                OracleDataReader reader = cmd.ExecuteReader();
                ds = new DataSet();
                oda = new OracleDataAdapter(cmd.CommandText, con);
                oda.Fill(ds);
                dataGridView1.DataSource = ds.Tables[0];
                dataGridView1.Columns["订货日期"].DefaultCellStyle.Format = "yyyy/MM/dd HH:mm:ss";//此句要放在ataGridView1.DataSource之后；
                con.Close();
            }
            catch (Exception E)
            { MessageBox.Show(E.Message); }
        }
 
        private void button1_Click(object sender, EventArgs e)
        {
            OracleCommandBuilder cx = new OracleCommandBuilder(oda);
            oda.Update(ds);
 
            con.Open();
            OracleCommand cmd = new OracleCommand("update stock set 订货日期=sysdate where 订货日期 is null", con);
            cmd.ExecuteNonQuery();
            MessageBox.Show("保存成功", "提示");
 
            //更新数据后刷新数据
            cmd = con.CreateCommand();
            cmd.CommandText = "select * from stock order by 订货日期 desc";
            OracleDataReader reader = cmd.ExecuteReader();
            ds = new DataSet();
            oda = new OracleDataAdapter(cmd.CommandText, con);
            oda.Fill(ds);
            dataGridView1.DataSource = ds.Tables[0];
            con.Close();
        }
    }
}