Solved

Comparing NULL to "" in MS Access

Posted on 2012-03-18
5
265 Views
Last Modified: 2012-04-09
ElseIf Me.fldURA_Class_Cat.Value = strOldValue And intAlreadyChanged = 1 Then

Is the code that is not firing properly, fldURA_Class_Cat.Value returns a value of NULL and strOldValue returns a value of "".  

Any suggestions???
0
Comment
Question by:rondawg
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
5 Comments
 
LVL 12

Accepted Solution

by:
danishani earned 500 total points
ID: 37735420
You can't compare a Null values to a Zero-length-String (""), which are two diferent things.

So in case you want to compare these, you can however convert the Null values to a zero-length-string.

Dim varNull As Variant

If IsNull(Me.fldURA_Class_Cat.Value) Then
 varNull = Me.fldURA_Class_Cat.Value & ""
End If

Hope this helps,
Daniel
0
 
LVL 42

Expert Comment

by:dqmq
ID: 37735421
ElseIf nz(Me.fldURA_Class_Cat.Value,"") = strOldValue And intAlreadyChanged = 1
0
 
LVL 20

Expert Comment

by:clarkscott
ID: 37738179
Remember, NULLS only refer to fields in tables, text boxes and other objects on forms, reports, etc.  "" refers ONLY to text(string) variables.

Scott C
0
 
LVL 42

Expert Comment

by:dqmq
ID: 37738686
>NULLS only refer to fields in tables, text boxes and other objects on forms, reports, etc.  "" refers ONLY to text(string) variables.

Were it only so simple. :>)
0
 
LVL 26

Expert Comment

by:Nick67
ID: 37754028
If you are coming from an Oracle background, you must be aware that Access/SQL Server do not share Oracle's convention for NULL.  Oracle uses "" to denote null for all datatype.  MS products do not.

I think too, looking at strOldValue that you are discovering, the hard way, that when the end user enters something in a control that was NULL and then backspaces to nothing, the value does not return to NULL, it is changed to "".  If they hit ESC, then it will return to NULL.

Now you have a fun little problem!  To the end user, NULL and "" look the same.  You'd probably be best putting a default value of "" in for the field in the table--that way NULL isn't part of the equation.  But there can be reasons not to do that.  So handle NULL on both sides of your test

ElseIf nz(Me.fldURA_Class_Cat.Value,"") = nz(strOldValue,"") And intAlreadyChanged = 1 Then

Now, no matter what initial state (NULL or "") it was in, you can do something with it if it is appearing blank to the end user.
0

Featured Post

Free Tool: SSL Checker

Scans your site and returns information about your SSL implementation and certificate. Helpful for debugging and validating your SSL configuration.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Introduction The Visual Basic for Applications (VBA) language is at the heart of every application that you write. It is your key to taking Access beyond the world of wizards into a world where anything is possible. This article introduces you to…
It’s the first day of March, the weather is starting to warm up and the excitement of the upcoming St. Patrick’s Day holiday can be felt throughout the world.
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…
Polish reports in Access so they look terrific. Take yourself to another level. Equations, Back Color, Alternate Back Color. Write easy VBA Code. Tighten space to use less pages. Launch report from a menu, considering criteria only when it is filled…

696 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