如何使用VB.Net连接更新查询？

Question

How do I Concatenate ProjFed (a string) with YrNbr (the value of a field in the data table) in an Update query? With my code as shown below I get an error that says: No value given for one or more required parameters.

cmd.CommandText = "UPDATE tblProjection SET YrFed1 = ProjFed & YrNbr"
cmd.ExecuteNonQuery()

I have tried all kinds of combinations and none of the have worked. I get various error messages.

Answer 1

I passed your variables to the procedure. I assumed both are strings because you are using the ampersand to concatenate them. The Using blocks make sure you database objects are closed and disposed.

I had to guess at what provider you are using. It could be OleDbConnection and Command or MySql etc.

You can pass the connection string directly to the constructor of the connection and, likewise, pass the command text and the connection directly to the constructor of the command.

Parameters help you avoid Sql Injection which can destroy your database. I also had to guess at the datatype of YrFed1. Check your database for the actual datatype.

VERY IMPORTANT!

As @Ken White mentioned in his comment. This Update statement will update every record in the table because there is no where clause.

Private Sub OPCode(ProjFed As String, YrNbr As String)
    Using cn As New SqlConnection("Your connection string"),
            cmd As New SqlCommand("UPDATE tblProjection SET YrFed1 = @Yr", cn)
        cmd.Parameters.Add("@Yr", SqlDbType.VarChar).Value = ProjFed & YrNbr
        cn.Open()
        cmd.ExecuteNonQuery()
    End Using
End Sub