没有为 1 个或多个必需参数提供值。更新 SQL

Question

我正在编写一个程序，当用户在列表视图中选择一条记录时，它会更新密码或积分。我收到一个错误“没有为 1 个或多个必需参数提供值”，我不知道如何纠正，我是否遗漏了一些明显的东西？

Dim sql As String = "UPDATE Users SET [Password] = @2,[LoyaltyPoints] = @3 WHERE [Username] = '" & mListView.SelectedItems(0).Text & "'"
cmd = New OleDbCommand(sql, con)

'ADD PARAMETER
cmd.Parameters.AddWithValue("@1", UpdatedUser)
cmd.Parameters.AddWithValue("@2", UpdatedPass)
cmd.Parameters.AddWithValue("@3", UpdatedPoints)


'OPEN CONNECTION,EXECUTE UPDATE,CLOSE CONNECTION'
Try
    con.Open()
    adapter = New OleDbDataAdapter(cmd)
    adapter.UpdateCommand = con.CreateCommand()
    adapter.UpdateCommand.CommandText = sql

    If (adapter.UpdateCommand.ExecuteNonQuery() = 0) Then 'Error Appears Here
        MsgBox("Successfully Updated")
        ClearAll()
    Else
        MsgBox("Unsuccessful")
     End If
     con.Close()
     Retrieve()

     Catch ex As Exception
         MsgBox(ex.Message)
         con.Close()
     End Try
End Sub

Answer 1

其他人已经指出了问题（和解决方案），但我想补充一点……避免命名参数 1、2、3 或 A、B、C。我敢打赌，如果你以与正在发送的数据相对应的方式命名它们，诊断问题会更容易。您在查询中缺少@1...但不要将其命名为@1：

Dim sql As String = "UPDATE Users SET [Password] = @PASS,[LoyaltyPoints] = @POINTS WHERE [Username] = @USER"
cmd = New OleDbCommand(sql, con)

cmd.Parameters.AddWithValue("@USER", UpdatedUser)
cmd.Parameters.AddWithValue("@PASS", UpdatedPass)
cmd.Parameters.AddWithValue("@POINTS", UpdatedPoints)

不要在伤口上撒盐，但你的解决方案是倒退了一大步。各项参数都不错。它们更适合数据库、更简洁的代码、完全安全，并且它们可以处理异常数据，例如，如果您传递的任何值中有单引号字符（如果发生这种情况，您的解决方案将崩溃​​）。

Answer 2

代码应该是这样的：

Dim updatedUser = mListView.SelectedItems(0).Text

Dim sql As String = "UPDATE Users SET [Password] = @pass, [LoyaltyPoints] = @points WHERE [Username] = @username"

Using conn As New OleDbConnection("your connection string"),
        cmd As New OleDbCommand(sql, conn)

    'TODO: Use the correct values for each .OleDbType and .Size parameter.
    cmd.Parameters.Add(New OleDbParameter With {.ParameterName = "@pass", .OleDbType = OleDbType.VarWChar, .Size = 99, .Value = updatedPass})
    cmd.Parameters.Add(New OleDbParameter With {.ParameterName = "@points", .OleDbType = OleDbType.Integer, .Value = updatedPoints})
    cmd.Parameters.Add(New OleDbParameter With {.ParameterName = "@username", .OleDbType = OleDbType.VarWChar, .Size = 99, .Value = updatedUser})

    Try
        conn.Open()

        If cmd.ExecuteNonQuery() = 0 Then
            MsgBox("Unsuccessful")
            ClearAll()
        Else
            MsgBox("Successfully Updated")
        End If

        Retrieve()

    Catch ex As Exception
        MsgBox(ex.Message)
    End Try

End Using

Answer 3

我明白了，我必须对 SQL 文本进行调整

        Dim sql As String = "UPDATE Users SET [Password] = '" + UpdatedPass + "',[LoyaltyPoints] = '" + UpdatedPoints + "' WHERE [Username] = '" & mListView.SelectedItems(0).Text & "'"
        cmd = New OleDbCommand(sql, con)

        'OPEN CONNECTION,EXECUTE UPDATE,CLOSE CONNECTION'
        Try
            con.Open()
            adapter = New OleDbDataAdapter(cmd)
            adapter.UpdateCommand = con.CreateCommand()
            adapter.UpdateCommand.CommandText = sql

            If (adapter.UpdateCommand.ExecuteNonQuery() > 0) Then
                MsgBox("Successfully Updated")
            Else
                MsgBox("Unsuccessful")
            End If
            con.Close()
            Retrieve()

        Catch ex As Exception
            MsgBox(ex.Message)
            con.Close()
        End Try