c＃update如果记录存在，则插入新记录

当用户在页面上的三个框中输入特定值时，我有代码将数据插入表中。

这些方框是订单号，总重量和跟踪参考。

我现在需要为此代码添加更多function，并首先检查订单号是否存在，如果需要更新列，如果不是，我需要插入新行并向其添加数据。

我想的很简单，比如IF results = 0，Insert NEW，ELSE update

如何修改我的代码才能执行此操作？

protected void Page_Load(object sender, EventArgs e) { errorLabel.Visible = false; successLabel.Visible = false; errorPanel.Visible = false; } protected void submitBtn_Click(object sender, EventArgs e) { if (Page.IsValid) { int _orderID = Convert.ToInt32(orderID.Text); string _trackingID = trackingNumber.Text; DateTime _date = DateTime.UtcNow; int _weightID = Convert.ToInt32(weightID.Text); SqlConnection myConnection = new SqlConnection("Data Source=localhost\\Sqlexpress;Initial Catalog=databasename;User ID=username;Password=password"); SqlCommand myCommand = new SqlCommand("INSERT into Shipment (TrackingNumber, OrderId, ShippedDateUtc, CreatedOnUtc, TotalWeight) VALUES (@tracking, @order, @date, @date, @weight)", myConnection); try { myConnection.Open(); myCommand.Parameters.AddWithValue("@order", _orderID); myCommand.Parameters.AddWithValue("@tracking", _trackingID); myCommand.Parameters.AddWithValue("@date", _date); myCommand.Parameters.AddWithValue("@weight", _weightID); int rowsUpdated = myCommand.ExecuteNonQuery(); myConnection.Close(); if (rowsUpdated > 0) { alertdiv.Attributes.Add("class", "alert alert-success form-signin"); successLabel.Text = "Thank you, tracking details have been updated"; successLabel.Visible = true; errorPanel.Visible = true; } else { alertdiv.Attributes.Add("class", "alert alert-error form-signin"); errorLabel.Text = "Oh dear, the order number is not recognised, please check and try again"; errorLabel.Visible = true; errorPanel.Visible = true; } orderID.Text = ""; trackingNumber.Text = ""; weightID.Text = ""; } catch (Exception f) { errorLabel.Text = "This order number does not exist, please check"; errorLabel.Visible = true; errorPanel.Visible = true; return; } } } protected void Signout_Click(object sender, EventArgs e) { FormsAuthentication.SignOut(); Response.Redirect("Login.aspx"); } 

Answer 1

您可以在INSERT语句之前添加一些SELECT查询。 因此，如果SELECT查询返回多行，则表示您已在DB中拥有该记录，并且需要更新。 所以，一般来说就像

 SqlCommand cmdCount = new SqlCommand("SELECT count(*) from Shipment WHERE OrderId = @order", myConnection); cmdCount.Parameters.AddWithValue("@order", _orderID); int count = (int)cmdCount.ExecuteScalar(); if (count > 0) { // UPDATE STATEMENT SqlCommand updCommand = new SqlCommand("UPDATE Shipment SET TrackingNumber = @tracking, ShippedDateUtc = @date, TotalWeight = @weight", myConnection); updCommand.Parameters.AddWithValue("@order", _orderID); updCommand.Parameters.AddWithValue("@tracking", _trackingID); updCommand.Parameters.AddWithValue("@date", _date); updCommand.Parameters.AddWithValue("@weight", _weightID); int rowsUpdated = myCommand.ExecuteNonQuery(); } else { // INSERT STATEMENT SqlCommand insCommand = new SqlCommand("INSERT into Shipment (TrackingNumber, OrderId, ShippedDateUtc, CreatedOnUtc, TotalWeight) VALUES (@tracking, @order, @date, @date, @weight)", myConnection); insCommand.Parameters.AddWithValue("@order", _orderID); insCommand.Parameters.AddWithValue("@tracking", _trackingID); insCommand.Parameters.AddWithValue("@date", _date); insCommand.Parameters.AddWithValue("@weight", _weightID); int rowsUpdated = myCommand.ExecuteNonQuery(); } 

编辑：或更短：

 SqlCommand command; if (count > 0) { command = new SqlCommand("UPDATE Shipment SET TrackingNumber = @tracking, ShippedDateUtc = @date, TotalWeight = @weight WHERE OrderId = @order", myConnection); } else { command = new SqlCommand("INSERT into Shipment (TrackingNumber, OrderId, ShippedDateUtc, CreatedOnUtc, TotalWeight) VALUES (@tracking, @order, @date, @date, @weight)", myConnection); } command.Parameters.AddWithValue("@order", _orderID); command.Parameters.AddWithValue("@tracking", _trackingID); command.Parameters.AddWithValue("@date", _date); command.Parameters.AddWithValue("@weight", _weightID); int rowsUpdated = command.ExecuteNonQuery(); 

Answer 2

最有效的方法是将function放入存储过程，例如（伪代码）： IF EXISTS(SELECT * FROM Orders WHERE OrderNo = @orderNo) UPDATE ...

ELSE INSERT ...

如果无法创建新的存储过程，则还可以创建包含此Statement的命令，但可读性通常更差。
这两种方法只需要一个DB请求。