The user not able to submit the Form and get the Error: “Invalid use of Null”

问题

My Project is developed in MS-Access 2010 and Back end is SQL Server 2016.I connect the back end with ODBC. I install the system in my PCs and it working good but in one PC, whenever the user try to submit he get the same error

! [Error image] https://ibb.co/fCV6JGF

I delete the old ODBC connection and create a "New" connection through SQL Server.Before I replace the Source code folder with new one.But the same Error occur.

Private Sub cmdPostSubmit_Click()
 postSubmit = 1
 postOnly = 0

 If TestOutlookIsOpen = True Then
Else
 If UCase (Trim(Me.cboAllStatus.Value)) = "STEPPED UP" Then
   MsgBox "Outlook is not open", vbCritical + vbOKOnly
   Exit Sub
 End If
End If

If (Nz(Trim(DLookup("fldAllStatus", "TBL_REQUEST_STATUS","fldTrackNo=
 '" & gTrackNo & "'"))) = "Unprocessed") 
  Then Msgbox "attach the docs",vbCritical + vbOKOnly
Exit Sub  
If Me.cmdPostSubmit.Caption = "Submit" Then

  If (Trim(DLookup("fldUnitName", "TBL_USER", "fldNetID = '" & Trim(gNetID) & "'")) = Trim(hostUNIT)) Then

         'If (Nz(DLookup("count(fldTrackNo)", "TBL_FILE_ATTACHMENT", "fldTRackNo = '" & gTrackNo & "'")) = 0 And Me.chkRet.Value = 0) Then
         '   MsgBox "This request must be returned and cannot be processed due to lack of attachments.", vbInformation + vbOKOnly
         '   Exit Sub
         'End If

         If (Me.chkRet.Value = -1) Then

             If MsgBox("Are your sre you want to return this request unrpocessed ?", vbQuestion + vbYesNo) = vbYes Then

                   If Nz(Me.txtRemarks.Value) = "" Then
                      MsgBox "Please write something in the remarks to proceed ... ", vbInformation + vbOKOnly
                      Exit Sub
                   Else
                      'Save the current request status prior to updating
                      saveUnprocessedStatus gTrackNo, Trim(DLookup("fldAllStatus", "TBL_REQUEST_STATUS", "fldTrackNo = '" & gTrackNo & "'"))
                      CurrentDb.Execute "UPDATE TBL_REQUEST_STATUS SET fldAllStatus = 'Unprocessed',fldReqStatus = 'Unprocessed'  WHERE fldTrackNo = '" & gTrackNo & "'"
                      CurrentDb.Execute "UPDATE TBL_REQUEST_APPROVAL SET fldReqStatus = 'Unprocessed'  WHERE fldTrackNo = '" & gTrackNo & "'"
                   End If

             Else
               Exit Sub
             End If

         End If

         If Nz(Me.txtRemarks.Value) = "" Then
            MsgBox "Please write something in the remarks ... ", vbInformation + vbOKOnly
            Exit Sub
         End If

  End If

  updateValuesDetails  'Download and update the details
  MsgBox "Request Successfully Posted And Submitted !!!", vbInformation + vbOKOnly

  If UCase(Trim(Me.cboAllStatus.Value)) = "STEPPED UP" Then
     clsMail.sendMailForStepUpRequest
  End If


 Else

    uploadValuesDetails  'Download and save the details
    MsgBox "Request Successfully Posted And Submitted !!!", vbInformation + vbOKOnly

  If UCase(Trim(Me.cboAllStatus.Value)) = "STEPPED UP" Then
     clsMail.sendMailForStepUpRequest
  End If


    disableMainButt 0
    Forms![FRM_MAIN].Form.cmdNewRequest.SetFocus
    Forms![FRM_MAIN]![subForm].SourceObject = "FRM_REQ_STATUS"

    '' RELOAD MASTER LIST
    strSQL = "SELECT TBL_REQUEST_STATUS.fldTrackNo,TBL_REQUEST_STATUS.fldJobTitle, TBL_REQUEST_STATUS.fldReqStatus,  TBL_REQUEST_STATUS.fldDateInitiated,"
    strSQL = strSQL & "TBL_REQUEST_STATUS.fldReqBy, TBL_REQUEST_STATUS.fldUnitApp, TBL_REQUEST_STATUS.fldEDURec, TBL_REQUEST_STATUS.fldEDUApp,"
    strSQL = strSQL & "TBL_REQUEST_STATUS.fldPercentage, TBL_WORKFLOW_APPROVAL.fldUnitApproved, TBL_WORKFLOW_APPROVAL.fldEDUEvaluated, TBL_WORKFLOW_APPROVAL.fldEDUApproved,"
    strSQL = strSQL & "TBL_WORKFLOW_APPROVAL.fldDivApproved,TBL_REQUEST_APPROVAL.fldNetID,TBL_WORKFLOW_APPROVAL.fldAssignedEngr,TBL_REQUEST_STATUS.fldAllStatus,TBL_REQUEST_STATUS.fldAllperc,TBL_REQUEST_STATUS.fldAllRemarks FROM 

  TBL_REQUEST_APPROVAL RIGHT JOIN (TBL_WORKFLOW_APPROVAL RIGHT JOIN    TBL_REQUEST_STATUS ON TBL_WORKFLOW_APPROVAL.fldTrackNo = TBL_REQUEST_STATUS.fldTrackNo)  ON TBL_REQUEST_APPROVAL.fldTrackNo = TBL_REQUEST_STATUS.fldTrackNo  "
    'strSQL = strSQL & "TBL_WORKFLOW_APPROVAL.fldDivApproved FROM TBL_WORKFLOW_APPROVAL RIGHT JOIN TBL_REQUEST_STATUS ON TBL_WORKFLOW_APPROVAL.fldTrackNo = TBL_REQUEST_STATUS.fldTrackNo "

    If IsCADOPR2(gNetID) Then
      Forms![FRM_MAIN]![subForm]![subForm3].Form.RecordSource = strSQL   & "   WHERE (TBL_REQUEST_STATUS.fldAllStatus <> 'Completed' AND  TBL_REQUEST_STATUS.fldAllStatus <> 'Cancelled' AND  TBL_REQUEST_STATUS.fldAllStatus <> 'Unprocessed') 

AND  (fldCADopr = '" & gNetID & "' OR fldCAD1 = '" & gNetID & "' OR  fldCAD2  = '" & gNetID & "' OR fldCAD3 = '" & gNetID & "' OR fldCAD4 = '" &  gNetID & "') ORDER BY TBL_REQUEST_STATUS.fldDateInitiated DESC" 'OR fldReqBy = '" & gNetID & "') AND fldUnitName = '" & gUnitDesc & "'"
    ElseIf IsEDUMember(gNetID) Then
       If Trim(DLookup("fldPosLevel", "TBL_USER", "fldNetID = '" & Trim (gNetID) & "'")) = "DRAFTSMAN" Then
           Forms![FRM_MAIN]![subForm]![subForm3].Form.RecordSource = strSQL  & " WHERE  TBL_WORKFLOW_APPROVAL.fldAssignedEngr = '" & gNetID & "' AND  TBL_REQUEST_STATUS.fldAllStatus <> 'Completed' AND TBL_REQUEST_STATUS.fldAllStatus <> 'Cancelled' AND TBL_REQUEST_STATUS.fldAllStatus <> 'Unprocessed' ORDER BY TBL_REQUEST_STATUS.fldDateInitiated DESC"
       Else
           Forms![FRM_MAIN]![subForm]![subForm3].Form.RecordSource =   strSQL & " WHERE TBL_REQUEST_STATUS.fldAllStatus <> 'Completed' AND TBL_REQUEST_STATUS.fldAllStatus <> 'Cancelled' AND  TBL_REQUEST_STATUS.fldAllStatus <> 'Unprocessed' ORDER BY TBL_REQUEST_STATUS.fldDateInitiated DESC"
       End If
    Else
      Forms![FRM_MAIN]![subForm]![subForm3].Form.RecordSource = strSQL   & "   WHERE fldUnitName = '" & gUnitDesc & "' AND   TBL_REQUEST_STATUS.fldAllStatus <> 'Completed' AND    TBL_REQUEST_STATUS.fldAllStatus <> 'Cancelled' AND 
 TBL_REQUEST_STATUS.fldAllStatus <> 'Unprocessed' ORDER BY      TBL_REQUEST_STATUS.fldDateInitiated DESC"
    End If


End If

 setUpAccessLevel

End Sub

On Clicking the Submit it will be saved in the SQL database but it throw the error message.

回答1:

As a general rule, anytime you going to run reports, query additional data, you would do BEYOND well to FIRST save the current record in the current context. In addition, if this is a new record, then un-like Access tables, the default values, and PK generation does NOT occur until such time you saved the current record.

so, in you code, you want to safe tuck away the current record. This will allow SQL server to setup the PK values and any default columns. So

Private Sub cmdPostSubmit_Click()
 postSubmit = 1
 postOnly = 0

 If me.Dirty = True then me.Dirty = False   ' save current record to table.

The other issue is does your code work for existing records, and not new ones, or does it always error out?

来源：https://stackoverflow.com/questions/57569272/the-user-not-able-to-submit-the-form-and-get-the-error-invalid-use-of-null