สอบถามการตรวจสอบค่าที่ซ้ำกันในตาราง เมื่อมีการ Insert , Update , Delete vb.net

    Private Sub btnSave_Click(sender As Object, e As EventArgs) Handles btnSave.Click
        Dim Conn As New OleDbConnection(strConnection)
        Dim Comm As New OleDb.OleDbCommand()

        Conn.Open()
        Dim intNumRows As Integer
        Dim i As Integer

        i = DataGridView1.CurrentRow.Index
        Dim strSQL As String
        strSQL = "SELECT count(*) from  [GROUP_USERS] gu WHERE gu.[GROUP_USER_ID] = '" & Me.DataGridView1.Item(2, i).Value.ToString() & "' "
        Comm = New OleDbCommand(strSQL, Conn)
        intNumRows = Comm.ExecuteScalar()

        If intNumRows > 0 Then
            'MessageBox.Show("มี USER นี้แล้ว.")
            'Else
            Dim strSQL2 As String
            strSQL2 = "INSERT INTO GROUP_USERS ([GROUP_USER],[USER_NAME],[Create_User],[Create_Date]) " &
            " VALUES " &
            " ('" & Me.TextBox1.Text & "','" & Me.DataGridView1.Item(1, i).Value.ToString() & "', '" & Label6.Text & "' , getdate() )"

            Comm = New OleDbCommand
            With Comm
                .Connection = Conn
                .CommandText = strSQL2
                .CommandType = CommandType.Text
                .ExecuteNonQuery()
            End With
            MessageBox.Show("เพิ่ม USER นี้แล้ว.")
        Else
            Dim strSQL3 As String
            strSQL3 = ""
            Me.DataView()
        End If

    End Sub