"Undefined function" error when accessing query with custom function using VB/DAO

Posted on 2003-11-12
Last Modified: 2008-02-01
I have an application in VB6 which works on an Access 97 database using DAO.

After discovering a bug with the datepart function I have included a custom function (saved in a module in the .mdb) to correctly calculate a week number.
However in the VB6 app any time I use SQL (i.e. to open a recordset) which uses a query with this custom function I get an "Undefined function" error.

As I understand this is because DAO cannot "see" the function as saved in the database and so cannot resolve the SQL (but it can see the built-in functions such as datepart).
Does anyone know how I can get around this problem?

I have tried writing the function into a .dll and referencing this in the database rather than having the code in a module in the .mdb but when I do this the query does not see the function in Access.

Any help would be appreciated.
Question by:Chris_Forsyth
  • 4
  • 3
LVL 44

Expert Comment

ID: 9733906
from a VB6 program, you CANNOT use any functions that are defined in the Access modules.  You will need to copy the Access Module code into your VB 6 application.


Author Comment

ID: 9738270
Problem is that I have a situation like this (example):

Field1 : Product - Text
Field2 : Volume produced- Long

Uses table to do calculation on volume produced

In VB program, have SQL with Query1 (i.e. using the stored query, as saved in access).  If I then have an action query using Query1 as the source and I try to run this under VB6, obviously the problem as discussed.  Unfortunately I use stored queries from the access .mdb quite a bit in my application, is this bad practice????  This way I do the work in a stored query (i.e. calculations) and use that stored query in my application.  So unfortunately I think I may be scuppered, even if I have the function in my VB application, as I am trying to use a stored query that has that function DAO will not be able to see it.  Is this correct??
LVL 44

Expert Comment

ID: 9738930
post the SQL of the QUERY, from Access.  What FUNCTION are you trying to execute?

POST the VB code as well.

How to run any project with ease

Manage projects of all sizes how you want. Great for personal to-do lists, project milestones, team priorities and launch plans.
- Combine task lists, docs, spreadsheets, and chat in one
- View and edit from mobile/offline
- Cut down on emails


Author Comment

ID: 9739203

The function I am calling is called "WeekNumber" (below), this calls the function "Days" (also below).  This is the function given by microsoft to cover the bug in the DatePart function (as in the knowledge based article below).


Public Function WeekNumber(InDate As Date) As Integer
On Error GoTo ErrorTrap

  Dim DayNo As Integer
  Dim StartDays As Integer
  Dim StopDays As Integer
  Dim StartDay As Integer
  Dim StopDay As Integer
  Dim VNumber As Integer
  Dim ThurFlag As Boolean

  DayNo = Days(InDate)
  StartDay = WeekDay(DateSerial(Year(InDate), 1, 1)) - 1
  StopDay = WeekDay(DateSerial(Year(InDate), 12, 31)) - 1
  ' Number of days belonging to first calendar week
  StartDays = 7 - (StartDay - 1)
  ' Number of days belonging to last calendar week
  StopDays = 7 - (StopDay - 1)
  ' Test to see if the year will have 53 weeks or not
  If StartDay = 4 Or StopDay = 4 Then ThurFlag = True Else ThurFlag = False
  VNumber = (DayNo - StartDays - 4) / 7
  ' If first week has 4 or more days, it will be calendar week 1
  ' If first week has less than 4 days, it will belong to last year's
  ' last calendar week
  If StartDays >= 4 Then
     WeekNumber = Fix(VNumber) + 2
     WeekNumber = Fix(VNumber) + 1
  End If
  ' Handle years whose last days will belong to coming year's first
  ' calendar week
  If WeekNumber > 52 And ThurFlag = False Then WeekNumber = 1
  ' Handle years whose first days will belong to the last year's
  ' last calendar week
  If WeekNumber = 0 Then
     WeekNumber = WeekNumber(DateSerial(Year(InDate) - 1, 12, 31))
  End If
Exit Function

' Note : to trap faults within this procedure
Err.Raise vbObjectError + 1, "WeekNumber", Err.Description
Resume ExitRoutine
End Function

Public Function Days(DayNo As Date) As Integer
On Error GoTo ErrorTrap

  Days = DayNo - DateSerial(Year(DayNo), 1, 0)
Exit Function

' Note : to trap faults within this procedure
Err.Raise vbObjectError + 2, "Days", Err.Description
Resume ExitRoutine
End Function


The SQL I am running is an action query :

"INSERT INTO [tblAllBandageProductionByRendement(Calc)] ( UserName, Bandage, Year, PeriodType, Period, Production )
SELECT '" & strUserName & "' AS User, qryAllBandageProductionByRendement.Bandage, qryAllBandageProductionByRendement.Year, qryAllBandageProductionByRendement.[Period Type], qryAllBandageProductionByRendement.Period, qryAllBandageProductionByRendement.Prod
FROM qryAllBandageProductionByRendement;"

The problem is that the source query "qryAllBandageProductionByRendement" uses the WeekNumber function (in one of its source queries).  This is saved in a module in the .mdb file (plus I have a copy in the VB6 application).
If I open the .mdb file and run the query "qryAllBandageProductionByRendement" (which is a select query) it runs okay within the access environment.  Also the insert SQL runs fine within the access environment.  It is only when I use DAO/VB6 that I cannot run the insert SQL.  I believe DAO cannot resolve "qryAllBandageProductionByRendement" when one of its sub queries contains the function (it cannot see the access modules).

Like I said I tried compiling the weeknumber function in a .dll and referencing it from the access application as well, but that didn't work either.

The more I talk it through, the more I think I am going to have to re-design a bit of the application so I don't have dependance on queries held in access.  Don't think I will be able to solve it with Access/DAO/VB.

Let me know what you think.

Author Comment

ID: 9739220
Been reading the microsoft article and the other way I can resolve this is to check if the return from datepart is 53 and if so change this to 1.  Just wary this won't cover all circumstances (plus it seems a bit untidy).

If you agree that this is the only (easy) way then I will do this.
LVL 44

Accepted Solution

Arthur_Wood earned 125 total points
ID: 9739914
the problem is NOT that the query is held in Access, as that is GENERALLY the best approach.  The query, when stored in Access, has been 'pre-processed' and thus will always execute FASTER than the samea query passed as the direct SQL text from a VB program.  However, this assumes that the query DOES NOT rely on the use of USER-DEFINED functions.  If you MUST use a USER-DEFINED function, then the problem becomes very complex.

If your last comment will in fact solve the problem, then go for it.


Author Comment

ID: 9740942
Like you say, is complex.  I had originally not relied on any user defined functions, but the datepart bug has changed that (thanks microsoft!!).  Anyway, will do the "fiddle", and have to hope it works it most circumstances.

Cheers for your time.

Featured Post

Free Gift Card with Acronis Backup Purchase!

Backup any data in any location: local and remote systems, physical and virtual servers, private and public clouds, Macs and PCs, tablets and mobile devices, & more! For limited time only, buy any Acronis backup products and get a FREE Amazon/Best Buy gift card worth up to $200!

Join & Write a Comment

Most if not all databases provide tools to filter data; even simple mail-merge programs might offer basic filtering capabilities. This is so important that, although Access has many built-in features to help the user in this task, developers often n…
Introduction When developing Access applications, often we need to know whether an object exists.  This article presents a quick and reliable routine to determine if an object exists without that object being opened. If you wanted to inspect/ite…
Familiarize people with the process of utilizing SQL Server functions from within Microsoft Access. Microsoft Access is a very powerful client/server development tool. One of the SQL Server objects that you can interact with from within Microsoft Ac…
Basics of query design. Shows you how to construct a simple query by adding tables, perform joins, defining output columns, perform sorting, and apply criteria.

758 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

27 Experts available now in Live!

Get 1:1 Help Now