Dim Mydb As New ADODB.Recordset
Dim Mydb1 As New ADODB.Recordset
Dim Str_text As String
Private Sub Command1_Click()
    On Error Resume Next
    Static i As Integer '记数器
    Static L As Integer '记数器
    Dim Str_name As String
    Dim Str_password As String
    Dim Str_username As String
    Dim Str_userpassword As String
    Dim Remainday As Long
    Str_name = txt_name.Text
    Str_password = txt_password.Text

    Set Mydb = ExeCutesql("select user from user1 where user='" & Str_name & "'", Str_text)

    If Mydb.EOF Then
        MsgBox "你输入的用户名不存在，请重新输入！", vbOKOnly + 32, "注意"
        L = L + 1
        txt_name.SetFocus
        If L = 5 Then
            MsgBox "你已经多次输入错误的用户名,请查证后重新登陆！", vbOKOnly + 48, "注意"
            End
        End If
        Exit Sub
    Else
        Set Mydb1 = ExeCutesql("select user,pass from user1 where user='" & Str_name & "'", Str_text)
        Str_username = Trim(Mydb1.Fields(0))
        Str_userpassword = Trim(Mydb1.Fields(1))
        If Trim(Str_password) = Str_userpassword Then

            frm_main.Show
            Mydb.Close
            Mydb1.Close
            Set Mydb = Nothing
            Set Mydb1 = Nothing
            Unload Me
        Else
            MsgBox "你输入的密码错误，请重新输入！", vbOKOnly + 32, "注意"
            i = i + 1
            txt_password.SetFocus
            If i = 3 Then
                MsgBox "你输入的密码三次都不正确，本系统将关闭！", vbOKOnly + 48, "注意"
                End
            End If
            Exit Sub
        End If
    End If

End Sub
Private Sub Command2_Click()
    Unload Me
End Sub

Private Sub txt_name_KeyDown(KeyCode As Integer, Shift As Integer)
    If KeyCode = 13 Then txt_password.SetFocus

End Sub

Private Sub txt_password_KeyPress(KeyAscii As Integer)
    If KeyAscii = 13 Then Command1.SetFocus
End Sub

Private Sub txt_name_LostFocus()
    Cname = txt_name.Text
End Sub

调试通过了，功能都可以实现，删除某些代码后功能依然能实现，是否代表那些代码就是多余的？