为什么我的sql命令给我一个错误的数据类型错误

Question

This is my code

 OleDbCommand cmd = new OleDbCommand("UPDATE Patient SET FirstName ='" + tbPatientFirstName.Text + "' WHERE PatientID='" + tbPatientID+ "' ",conn);

The text I'm an changing in the tbPatientFirstName is from a string to a string. The PatientID is the records primary key. I know I'm not using parameterised sql but its not required and I don't have time to learn it at the moment

Answer 1

Apart from the suggestion to use paramterized query (which you believe is not needed, so hopefully it is OK), three things seem to be the potential causes of the error.

First, you seem to use the TextBox object rather than its Text . Change tbPatientID to tbPatientID.Text

Secondly, if your PatientID is integer, you may need to remove the apostrophe ' for the tbPatientID

WHERE PatientID=" + tbPatientID.Text.Trim()+ " " //no apostrophe

Thirdly, to avoid having whitespace undetected, consider using Trim() :

OleDbCommand cmd = new OleDbCommand("UPDATE Patient SET FirstName ='" + tbPatientFirstName.Text.Trim() + "' WHERE PatientID=" + tbPatientID.Text.Trim()+ " ",conn);

Answer 2

The time required to use a parameterized query is a lot less than the time required to fix these errors

OleDbCommand cmd = new OleDbCommand(@"UPDATE Patient 
       SET FirstName =@name WHERE PatientID= @id", conn);

cmd.Parameters.Add("@name", OleDbType.VarWChar).Value = tbPatientFirstName.Text 
cmd.Parameters.Add("@id", OleDbType.Integer).Value = Convert.ToInt32(tbPatientID.Text);

And that's all is required. Now you don't have troubles in passing values to your database engine also if these values contains a single quote.