Understanding the Null

[steve711]

Hello All,

I have a form that has a text box that if left blank, untouched, should be read as an error to the user.

For example. They must enter a tail number in this block if they entered a flight time for that tail number.

My problem arises when in my code I do this.

If me.txtEcoTime.value > 0 and me.txtEcoStar.value = Null then (slap the user to enter a tail number setting focus to that offending block)

Ok this doesn't work for some reason. I've watched it and Access sees that txtEcoStar = Null but when I do this check it could careless. What am I missing or doing wrong on this one?

 

[DALeffler]

From the IsNull function description in Access 97 help:

Important: Use the IsNull function to determine whether an expression contains a Null value. Expressions that you might expect to evaluate to True under some circumstances, such as If Var = Null and If Var <> Null, are always False. This is because any expression containing a Null is itself Null and, therefore, False.

So to test for Null, try:

If Me.txtEcoTime > 0 And IsNull(Me.txtEcoStar) Then
ArgueWithUser
End If

hth,

Doug.

 

[steve711]

Thanks

Thank you. That solved that minor headache. I looked in Office XP Access help and was unable to find what you found unless I specifically looked for IsNull. Just Null doesn't do the trick. But anyway.

Thank you again.

 

[dcx693]

As you two have figured out, perhaps accidentally, the Access 97 help system is far superior to the Access 2000/20002 (XP) system. It's been discussed on the forums before. I don't know what Microsoft did, but hopefully they fixed 2003.

 

[DALeffler]

Ah-yup!

'97 & 2000 Helps are different, no doubt...

I dunno... Designing a help for a 'puter has gotta be one of the hardest things there is to do (I usually quit 'bout half way through a help file for a db 'casue I don't know where to stop giving info. to a user...).

All in all, I'd have to say neither '97 or 2000 Help is that bad.

And neither one is that good.

Anyone remember running code & looking up err numbers in (heh, heh...) ring binders?

I do. It's really all the same thing: Ya gotta follow references...

Doug.