a form works wierd

[Oblivion_Creed]

Hello, my project is big (over 10mb) so i uploaded it to drive: https://drive.google.com/file/d/1VA4...ew?usp=sharing

In the form "frmBorrow" there is a button with a macro.

in that macro there's this condition:
ElseIf (DLookup("[LibraryID]", "tblCurrentUser") - DLookup("[libraryID]", "tblBooks") = 0) Then
Beep


MsgBox "The given book dosen't exist in YOUR library", vbOKOnly, "error"

i ment in here to check if the book is in the same library as the user but it doesn't work.

can any one help me fix it?

[Bulzie]

What do you mean by does not work, does it give error or does not return data?

I think you need the where part of DLookup or how does it know which record and LIbraryID to choose? Maybe:
(DLookup("[LibraryID]", "tblCurrentUser", "LibraryID = " & CurrentLibraryID) - DLookup("[libraryID]", "tblBooks", "LibraryID = " & CurrentLibraryID) = 0)

CurrentLibraryID might be from your recordset or value on form, etc. I just named it that but you need to put right name and syntax there.

[aytee111]

Macros are cumbersome and restrictive. Click on the Convert to VBA button, it will be easier to read and to troubleshoot.

[Micron]

ElseIf DLookup("[LibraryID]", "tblCurrentUser") <> DLookup("[libraryID]", "tblBooks") Then
Without the criteria part, DLookup will stop at the first record where the field is not null (unless I'm wrong about that and it will stop at the first record - period).
Aside from that, the expression posted basically says, if LibraryID in table A minus LibraryID in table B = 0, then do what follows because it's true. If the id's are text, then unless they can be treated as numbers, you're trying to subtract 2 words from each other. If the id's are autonumbers, you shouldn't be trying to do anything with them. If they are numbers, then just compare them instead of doing arithmetic on them.

[Oblivion_Creed]

What do you mean by does not work, does it give error or does not return data?

I think you need the where part of DLookup or how does it know which record and LIbraryID to choose? Maybe:
(DLookup("[LibraryID]", "tblCurrentUser", "LibraryID = " & CurrentLibraryID) - DLookup("[libraryID]", "tblBooks", "LibraryID = " & CurrentLibraryID) = 0)

CurrentLibraryID might be from your recordset or value on form, etc. I just named it that but you need to put right name and syntax there.

Macros are cumbersome and restrictive. Click on the Convert to VBA button, it will be easier to read and to troubleshoot.

ElseIf DLookup("[LibraryID]", "tblCurrentUser") <> DLookup("[libraryID]", "tblBooks") Then
Without the criteria part, DLookup will stop at the first record where the field is not null (unless I'm wrong about that and it will stop at the first record - period).
Aside from that, the expression posted basically says, if LibraryID in table A minus LibraryID in table B = 0, then do what follows because it's true. If the id's are text, then unless they can be treated as numbers, you're trying to subtract 2 words from each other. If the id's are autonumbers, you shouldn't be trying to do anything with them. If they are numbers, then just compare them instead of doing arithmetic on them.

The code should check if the librarian who's trying to borrow the book is in the same library as the book...
the code i tried using and your codes allowed the librarian borrow books from different library or didn't allow it to borrow book from and library

[Micron]

I was trying to make the point that without where criteria your expression couldn't work regardless. If no one can help you soon I'll look at it further when I get home. Not going to try this on my phone.

[davegri]

In your db,
LibraryID in tblLibraries is a number, like 1,2,3
LibraryID in tblBooks and tblCurrentUser is a text field containing Arabic characters. It should be numeric, containing a value (1,2,3) equal to a key in tblLibraries.
None of your user defined tables are set up in the relationship window. You need to get all of this straight before making queries or even forms or reports.