我正在使用 c# 开发一个表单应用程序，其中有一个表，我在我的数据库中定期更新相同的数据有一个名为 customers 的表具有以下列
客户 ID | 余额 | Last_Bill_Id | Last_Bill_Date | Last_Bill_Total | Last_Deposited | Last_Deposited_Date |
现在我正在使用这段代码来更新我的数据库
try
{
OleDbConnection con = new OleDbConnection("Provider = Microsoft.Jet.OLEDB.4.0; Data Source = G:\\my Documents\\Visual Studio 2008\\Projects\\xml_and_db_test\\xml_and_db_test\\bin\\Debug\\database_for_kissan_Pashu_AhaR_Bills.mdb");
string queryText = "UPDATE Customers SET Balance = ? ,Last_Bill_Id = ?,Last_Bill_Date = ? ,Last_Bill_Total = ?,Last_Deposited = ? , Last_Deposited_Date =? where CustomerId = ?;";
OleDbCommand cmd = new OleDbCommand(queryText, con);
cmd.CommandType = CommandType.Text;
cmd.Parameters.Add("Balance", OleDbType.Integer).Value = Convert.ToInt32(textBox2.Text);
cmd.Parameters.Add("Last_Bill_Id", OleDbType.Integer).Value = 15;
cmd.Parameters.Add("Last_Bill_Date", OleDbType.Date).Value = DateTime.Now;
cmd.Parameters.Add("Last_Bill_Total", OleDbType.Integer).Value = 1560;
cmd.Parameters.Add("Last_Deposited", OleDbType.Integer).Value = 500;
cmd.Parameters.Add("Last_Deposited_Date", OleDbType.Date).Value = DateTime.Now;
cmd.Parameters.Add("CustomerId", OleDbType.Integer).Value = Convert.ToInt32(textBox1.Text);
con.Open(); // open the connection
//OleDbDataReader dr = cmd.ExecuteNonQuery();
int yy = cmd.ExecuteNonQuery();
textBox3.Text = "update Done";
con.Close();
}
catch (Exception ex)
{
string c = ex.ToString();
MessageBox.Show(c);
}
问题 有时我不想更新Last_Deposited 和 Last_Deposited_Date 字段然后我尝试了这段代码
try
{
OleDbConnection con = new OleDbConnection("Provider = Microsoft.Jet.OLEDB.4.0; Data Source = G:\\my Documents\\Visual Studio 2008\\Projects\\xml_and_db_test\\xml_and_db_test\\bin\\Debug\\database_for_kissan_Pashu_AhaR_Bills.mdb");
string queryText = "UPDATE Customers SET Balance = ? ,Last_Bill_Id = ?,Last_Bill_Date = ? ,Last_Bill_Total = ? where CustomerId = ?;";
OleDbCommand cmd = new OleDbCommand(queryText, con);
cmd.CommandType = CommandType.Text;
cmd.Parameters.Add("Balance", OleDbType.Integer).Value = Convert.ToInt32(textBox2.Text);
cmd.Parameters.Add("Last_Bill_Id", OleDbType.Integer).Value = 15;
cmd.Parameters.Add("Last_Bill_Date", OleDbType.Date).Value = DateTime.Now;
cmd.Parameters.Add("Last_Bill_Total", OleDbType.Integer).Value = 1560;
// cmd.Parameters.Add("Last_Deposited", OleDbType.Integer).Value = 500;
// cmd.Parameters.Add("Last_Deposited_Date", OleDbType.Date).Value = DateTime.Now;
cmd.Parameters.Add("CustomerId", OleDbType.Integer).Value = Convert.ToInt32(textBox1.Text);
con.Open(); // open the connection
//OleDbDataReader dr = cmd.ExecuteNonQuery();
int yy = cmd.ExecuteNonQuery();
textBox3.Text = "update Done";
con.Close();
}
catch (Exception ex)
{
string c = ex.ToString();
MessageBox.Show(c);
}
现在，每当我用第二个代码更新我的 dB 时，保存在 Last_Deposited 和 Last_Deposited_Date 中的值都会被删除，我不想删除这些值，只想在这些字段有新值可用时更新。