You haven't described your database's structure or relationships, but I
expect vendor informtion should be in its own table, and filename
information in a separate related table, linked through the VendorID.  That
is, VendorID is the primary key in the vendor table, and the foreign key in
the filename table.  The filename table could have its own primary key, or
it could have a primary key consisting of VendorID and FileName.
You say you "need to create a unique ID".  Changing the VendorID will cause
any relationships to stop working, so you need to find another way to make
the record unique.  Is there a reason for adding a letter suffix
specifically, or are you just trying to assure the record is unique?

Hi Ed,
I am not sure if I totally understand your meaning. Did you mean that you
just wanted to find a query to produce unique VendorID in the query result?

I saw that you wanted to use a letter A, B,..., etc to append to VendorID
value, however what is the postfix letter if one VendorID has more than 26
files matched?

Regarding your requirement, I think that using number as postfix instead of
letter would be better. You can write a function to do this. For example:
Public Function VendorUniqueID(currentVendorID As Integer) As String
   Static t_vendorId As Integer
   Static t_nCount As Long
   Dim strUniqueId As String
   
   If IsEmpty(t_nCount) Or IsEmpty(t_vendorId) Then
       t_vendorId = 0
       t_nCount = 0
   End If
   
   If t_vendorId <> 0 And t_vendorId = currentVendorID Then
       t_nCount = t_nCount + 1
   Else
       t_vendorId = currentVendorID
       t_nCount = 1
   End If
   
   strUniqueId = CStr(t_vendorId) & "." & CStr(t_nCount)
   
   VendorUniqueID = strUniqueId
End Function

Then you can save the following query as "qryVendorFile":
SELECT VendorUniqueID(VendorID) AS NewVendorID, FileName FROM VendorFile;

Then you can query the records as following:
 Dim db As DAO.Database
  Dim qdf As DAO.QueryDef
  Dim strSQL As String
  Set db = CurrentDb
  Set qdf = db.QueryDefs("qryVendorFile")

Hope this helps. If you have any other questions or concerns, please feel
free to let me know.

Best regards,
Charles Wang
Microsoft Online Community Support
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