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isnull inside of an iff statement MS Access

Posted on 2015-01-02
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Last Modified: 2015-01-02
I'm having some trouble working out using the isnull within an if statement (MS Access 2003).

Things looks roughly like this -
MEDMRKUP - MEDMIN - IVMRKUP - IVMIN: IIf([GEN_DISP_UNIT]="DPU",[MED_PVAR1_DPU],[MED_PVAR1_DPD])+".....
the [MED_PVAR1_DPU] and [MED_PVAR1_DPD] might be null.
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Question by:ghettocounselor
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Nick67 earned 500 total points
ID: 40528106
+ is usually ONLY used for numeric
& is the usual concatenator for strings

The thing is, that + can do some very, very neat things (in Access only) when null gets involved
@harfang wrote a very neat article about that here
http://www.experts-exchange.com/Database/MS_Access/A_2040-Concatenation-in-Access-Reports-and-Forms.html
Even if this is NOT something you are pursuing, this is worth reading.

Generally in Access, if something can be null and we have to deal with that, we use the Nz() function.
Nz is basically an isnull and if rolled together
Nz(ValueThatMayBeNull, WhatToReplaceTheNullValueWith)

Nz is the exact same as SQL Server's ISNull() function.
Where things get confusing is that Access also has an ISNull() function.
All it does, is return TRUE if that value is NULL and False if it is not.

ISNull(SomeNullValue) will equal TRUE
ISNull(SomeNonNullValue) will equal FALSE

I rarely use it -- because 99% of the time, if you are testing for null, you want to immediately deal with it -- and that's what Nz() is for!
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by:ghettocounselor
ID: 40528242
Decided on this tactic:
  = UCase([LastName]) & ', ' & [FirstName] & ' ' & [Initial] & '. (' & [Title] & ')'

This shows as "DOE, John A. (Dr)". This is nice unless there is no middle initial or no title: "DOE, John . ()". If needed, Null values can be converted using Nz(). For example, display "nmi" for "no middle initial" or "?" for missing title:

        ... & Nz([Initial], 'nmi')
from link in selected resolution.

seems to be working as expected:
MEDMRKUP - MEDMIN - IVMRKUP - IVMIN: IIf([GEN_DISP_UNIT]="DPU",Nz([MED_PVAR1_DPU],'ndpu'),Nz([MED_PVAR1_DPD],'ndpd'))+" ....
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by:Nick67
ID: 40528276
 = UCase([LastName]) & ', ' & [FirstName] & ' ' & [Initial] & '. (' & [Title] & ')'
That looks like a ControlSource for a textbox on a form.
That's a place where @Harfang's nice little trick will work
 = UCase([LastName]) & ', ' & [FirstName] + ' ' & [Initial] & '. ' + (' & [Title] & ')'
As a ControlSource for a textbox, this will collapse to "DOE, John"  when the initial and title are null

MEDMRKUP - MEDMIN - IVMRKUP - IVMIN: IIf([GEN_DISP_UNIT]="DPU",Nz([MED_PVAR1_DPU],'ndpu'),Nz([MED_PVAR1_DPD],'ndpd'))+" ....
This looks like it's from a query, and that's pretty much the only way to do it.
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