左连接Mysql查询导致错误

Question

我有一个mysql左连接查询。此查询运行正常。但左边加入的桌子没有获得价值。请通过以下查询。我在C＃工作

void getstuinfo()
        {
            try
            {
                MySqlCommand com = new MySqlCommand("select stumaster.stuname,"+
                "stumaster.lname,"+
                "stumaster.fname,"+
                "stumaster.mname,"+
                "stumaster.fa_calty,"+
                "stumaster.sex,"+
                "castmaster.castdisp,"+
                "stumaster.castcode,"+
                "stumaster.nwscs "+
                "from stumaster "+ 
                " left join castmaster  on stumaster.castcode = castmaster.castcode "+
                " where grno = " + Convert.ToInt32(textBox1.Text).ToString(), con_db.con);
                MySqlDataReader dr1 = com.ExecuteReader();
                if (dr1.HasRows)
                {
                    while (dr1.Read())
                    {
                        textBox2.Text = (dr1[("stuname")].ToString());
                        textBox4.Text = (dr1["lname"]).ToString();
                        textBox5.Text = (dr1["fname"]).ToString();
                        textBox6.Text = (dr1["mname"]).ToString();
                        comboBox5.Text = (dr1["fa_calty"]).ToString();
                        comboBox1.Text = (dr1["castdisp"]).ToString();
                        textBox7.Text = (dr1["castcode"]).ToString();
                        textBox9.Text = (dr1["nwscs"]).ToString();
                        string wsex = (dr1["sex"]).ToString();

                        if (wsex == "M")
                        {
                            radioButton1.Checked = true;
                        }
                        else
                        {
                            radioButton2.Checked = true;
                        }
                    }
                    dr1.Close();
                }
                else
                {
                    MessageBox.Show("Not a Valid G.R.No.", " Student Information ");
                    dr1.Close();
                    textBox1.Focus();
                    return;
                }
            }
            catch (FormatException)
            {
                MessageBox.Show("Date is Invalid  ");
            }
        }

Answer 1

你必须用grno

给表名

即

stumaster.grno   = conditiion