If I have an equation x=y&z (boolean AND) is there a way of rearranging this function so as y=x?z. In a similar fashion to normal algebra that x=y+z can be rearranged as y=x-z.
Similarly, can x=y|z (boolean OR) be rearranged to something y=x?z?
It is easy to prove that such inversion operators cannot exist.
For the AND case:
false = true & false ⇒ true = false ? false
false = false & false ⇒ false = false ? false
But false ? false cannot be true and false at the same time, so there cannot be an operator ? with the desired property. ∎
For the OR case:
true = true | true ⇒ true = true ? true
true = false | true ⇒ false = true ? true
But true ? true cannot be true and false at the same time, so there cannot be an operator ? with the desired property. ∎
Related
I have some code than download CSV/HTML data from webpages without any problem. The code is something similar to this:
With ActiveSheet.QueryTables.Add(Connection:="URL;" & conexion, Destination:=Range("A1"))
.Name = "FunctionRollupMTO"
.FieldNames = True
.RowNumbers = False
.FillAdjacentFormulas = False
.PreserveFormatting = True
.RefreshOnFileOpen = False
.BackgroundQuery = True
.RefreshStyle = xlOverwriteCells
.SavePassword = False
.SaveData = True
.AdjustColumnWidth = True
.RefreshPeriod = 0
.WebFormatting = xlWebFormattingNone
.WebPreFormattedTextToColumns = True
.WebConsecutiveDelimitersAsOne = True
.WebSingleBlockTextImport = False
.WebDisableDateRecognition = False
.WebDisableRedirections = False
.Refresh BackgroundQuery:=False
End With
The problem is than the webpage (originally in the variable conexion) is beeing updated and now the data is different. For downloading the data, there is a button for "Download CSV" but the link for that button is not always the same (the URL is generated every time the user press the button).
There is a way to emulate VBA to press that button? Or maybe a different way of connect to that webpage? I've been trying MSXML2 but sincerely I don't really understand its way of work.
Thanks!
In if statements I always have to use if isnull(x) or x = "" then
What is the difference between the two and why doesn't each of them work in some cases?
NULL is the absence of a value*
"" is a zero-length string
Due to implicit conversion - an object that hasn't been populated yet might return true for both cases. However if you were to place a value of "" in there, it would return False for isnull() and True for = ""
*Credit to Comintern for improving the explanation (see comments)
If you do that check, to makes sense x must be a Variant, and Null is not "Nothing". Nothing means Empty and a special check for that exists.
Run this and see:
Dim x As Variant
Debug.Print IsEmpty(x) ' True
Debug.Print IsNull(x) ' False
Debug.Print x = "" ' True
Debug.Print Nz(x) = "" ' True
x = Null
Debug.Print IsEmpty(x) ' False
Debug.Print IsNull(x) ' True
Debug.Print x = "" ' Null
Debug.Print Nz(x) = "" ' True
x = ""
Debug.Print IsEmpty(x) ' False
Debug.Print IsNull(x) ' False
Debug.Print x = "" ' True
Debug.Print Nz(x) = "" ' True
As said by the other answers, null is nothing, "" is an empty string.
To test for both null and empty variables in access VBA, use the following:
If nz([variable], "") = "" Then do stuff
The nz function converts null variables to "" or 0
when I want to check for a null/ empty string
I use
If x & "" <> "" then
isnull means the value is not known while edit: "" means it is zero-length string*
*Credit: #Macro Man.
I have a problem in hiding my buttons and not working mostly is when the button itself was clicked, it supposed to be hidden.
I have a code below from one of my buttons but most of the button visibility codes are not working. I tried to add:
DoEvents
but still don't work. I don't know what the problem is. Some Enable properties were working but some are not.
Private Sub cmdSave_Click()
If MsgBox("Are you sure to save record?", vbYesNo, "Save Record") = vbYes Then
DoEvents
imgPic.Enabled = False
txtLRN.Enabled = False
txtLN.Enabled = False
txtFN.Enabled = False
txtMN.Enabled = False
txtS.Enabled = False
txtA.Enabled = False
txtBD.Enabled = False
txtBP.Enabled = False
txtMT.Enabled = False
txtIP.Enabled = False
txtRG.Enabled = False
txtAH.Enabled = False
txtAB.Enabled = False
txtAM.Enabled = False
txtAP.Enabled = False
txtF.Enabled = False
txtM.Enabled = False
txtGN.Enabled = False
txtGR.Enabled = False
txtCN.Enabled = False
txtR.Enabled = False
DoEvents
cmdSearch.Visible = True
cmdFirst.Visible = True
cmdPrev.Visible = True
cmdNext.Visible = True
cmdNext.Visible = True
cmdLast.Visible = True
cmdNew.Visible = True
cmdDelete.Visible = True
cmdEdit.Visible = True
DoEvents
cmdSave.Visible = False
cmdCancel.Visible = False
DoEvents
End if
End Sub
This simplified version of your procedure will trigger error #2165, "You can't hide a control that has the focus."
Private Sub cmdSave_Click()
Me.cmdSave.Visible = False
End Sub
During cmdSave_Click, cmdSave has focus, so you can't hide it without first moving focus to another unhidden control. This version will avoid that error:
Private Sub cmdSave_Click()
Me.cmdSearch.Visible = True
Me.cmdSearch.SetFocus
Me.cmdSave.Visible = False
End Sub
In similar cases, I've found that you need to specify the form reference ("Me.").
So try (for example)
Me.cmdCancel.Visible = True
In other words specify "Me." in front of the control name.
I have a command button in a form that allows users to add a new record. The command only works the first time you click it after the form is opened. I can navigate through the records without any errors and the first time you add a record after the form is opened will not give errors. Once you try to add a second record, the "Can't go to the specified record" error message is displayed.
I can make edits in the query without a problem and I can edit things without a problem. If I close out of the form and reopen it I can add a new record without issues. Anyone have ideas?
Using VBA, it's the standard add-new code, nothing else. Posted all the code for this form below. Some of the command buttons listed are in macros, don't know if that makes a difference.
Private Sub add_Click()
DoCmd.GoToRecord , , acNewRec
End Sub
Private Sub edit_info_Click()
Date_of_Echo.Locked = False
ID.Locked = False
AoV.Locked = False
AI.Locked = False
MR.Locked = False
TR.Locked = False
TR_velocity.Locked = False
PA_pressures.Locked = False
LVeDD.Locked = False
LVeSD.Locked = False
RV_function.Locked = False
comments.Locked = False
Me.next.Visible = False
Me.previous.Visible = False
Me.first.Visible = False
Me.last.Visible = False
Me.add.Visible = False
Me.save.Visible = True
Me.save.SetFocus
Me.edit_info.Visible = False
End Sub
Private Sub Form_Current()
If Me.NewRecord Then
Me.recordcounter.Caption = "New Record"
Me.next.Visible = False
Me.previous.Visible = False
Me.first.Visible = False
Me.last.Visible = False
Me.add.Visible = False
Me.edit_info.Visible = False
Me.save.Visible = True
Date_of_Echo.Locked = False
ID.Locked = False
AoV.Locked = False
AI.Locked = False
MR.Locked = False
TR.Locked = False
TR_velocity.Locked = False
PA_pressures.Locked = False
LVeDD.Locked = False
LVeSD.Locked = False
RV_function.Locked = False
comments.Locked = False
Else
Me.recordcounter.Caption = "Record " & Me.CurrentRecord & " of " & Me.Recordset.RecordCount
Me.next.Visible = True
Me.previous.Visible = True
Me.first.Visible = True
Me.last.Visible = True
Me.add.Visible = True
Me.edit_info.Visible = True
Me.save.Visible = False
End If
End Sub
Private Sub save_Click()
DoCmd.save
Me.previous.Visible = True
Me.first.Visible = True
Me.last.Visible = True
Me.next.Visible = True
Me.add.Visible = True
Me.edit_info.Visible = True
Me.recordcounter.Caption = "Record " & Me.CurrentRecord & " of " & Me.Recordset.RecordCount
Me.add.SetFocus
Me.save.Visible = False
Date_of_Echo.Locked = True
ID.Locked = True
AoV.Locked = True
AI.Locked = True
MR.Locked = True
TR.Locked = True
TR_velocity.Locked = True
PA_pressures.Locked = True
LVeDD.Locked = True
LVeSD.Locked = True
RV_function.Locked = True
comments.Locked = True
End Sub
Private Sub next_Click()
On Error GoTo Err_cmdLastRecord_Click
Me.AllowAdditions = False
DoCmd.GoToRecord , , acNext
Exit_cmdLastRecord_Click:
Exit Sub
Err_cmdLastRecord_Click:
MsgBox " There are no more records ", vbExclamation, ""
Resume Exit_cmdLastRecord_Click
End Sub
My first thought is that your record isn't saving before you try to go to a new record so try this and see if it fixes the issue.
Private Sub add_Click()
If Me.Dirty Then
Me.Dirty = False
End If
DoCmd.GoToRecord , , acNewRec
End Sub
If anyone is still having this problem, I can't explain why it's happening, but here's a work around:
Reset the AllowAdditionsProperty on the form:
Me.[form_name].Form.AllowAdditions = False
Me.[form_name].Form.AllowAdditions = True
This was a very strange issue because my code had been working fine for weeks. I was using something like this:
Me.frm.SetFocus
DoCmd.GoToRecord , , acNewRec
!Field1 = value1
!Field2 = value2
It was working great, and then out of the blue I started getting the "Can't go to Specified Record" error, even though I had made no changes to the code. The form settings were fine and I could add records all day long in the underlying table. I even checked the form's AllowAdditions property in the Immediate window, and that showed it was set to True. But I tried this work around, and it worked.
Now I add those two lines after every instance of Docmd.GoToNewRoecord, acNewRecord and it's working.
Another thing I have mentioned with the same problem is that you should check the Form data source query. Are all the FIELDS available, are the JOINS correct?
In my case I changed indexed joins from text fields to numeric and it needed update also in Form Data source query.
I am trying to import comma separated numbers in a cell in excel. It looks like this on web:
000002678,000002737,000002827,000004326,000008528
But as soon as I import it in excel it transforms to following:
2,678,000,002,737,000,000,000,000,000,000,000,000,000
How can I maintain the format like it is on web and not treat it as one big number?
With ActiveSheet.QueryTables.Add(Connection:= _
"URL;http://localhost:65076/TestData", Destination:=Range( _
"$A$1"))
.Name = "Test"
.FieldNames = True
.RowNumbers = False
.FillAdjacentFormulas = False
.PreserveFormatting = True
.RefreshOnFileOpen = False
.BackgroundQuery = True
.RefreshStyle = xlInsertDeleteCells
.SavePassword = False
.SaveData = True
.AdjustColumnWidth = True
.RefreshPeriod = 0
.WebSelectionType = xlAllTables
.WebFormatting = xlWebFormattingNone
.WebPreFormattedTextToColumns = True
.WebConsecutiveDelimitersAsOne = True
.WebSingleBlockTextImport = False
.WebDisableDateRecognition = False
.WebDisableRedirections = False
.Refresh BackgroundQuery:=False
End With
#PeterL or user793468 Did you ever solve this? Because i have the exact same problem and the only solution i found was a workaround (that actually can work!)
Set Windows Region and Language settings: "Decimal Settings" from , to . and excel will not treat my case 016448,016501,017612,01... etc as one long number.
If you plan on running the script "autonomasly" then just have those settings in a virtual machine where you run the script.