A simple verification - create a form, put a button on it. In the click event, put:
Private Sub MyBtn_Click()

     msgbox ("" = " ")

End Sub


A zero-length string is just that. It's a string with nothing in it. Whereas a space is a string with one character in it. That's a space character, which is ASCII 32. And neither of those things are equal to NULL, which is no value. A zero-length string says "I know what the value is; it's blank", whereas null says "I don't know what the value is."

See: Zero Length

Ugh, sorry, video must not of registered when I tried to add it.  Was on way out door for doc appointment and didn't verify

I will talk about this in Friday's Quick Queries video: 599cd.com/QQ81

Hello Donald, hello Richard

Thanks for your rapid answers.
My problem is not about understanding Null Value etc. Thanks to the excellent!!! courses of Richard this is clear for me.

My question is:
There is a field "Value" that may contain a Null Value, a ZLS or a space.
The aim is to show by conditional formatting what kind of value it is.
To check this I have made database. The conditional formatting does not work for ZLS and space, the result is the same as for Null Value.
See picture attached.

Thanks again for your help.

Rolf

BTW. I am aware that Access is a "Space killer".

I got received similar results to your test when I tried just using native Access functions (simple comparison, strcomp as text, strcomp as binary, etc). I'm sure there is probably a better way to test, however, I got expected results by creating some simple VBA Functions to do the test there and using the function call in the conditional formatting.

Details

Public Function CheckNull() As Boolean
    
    CheckNull = False
    If IsNull(Text0) Then CheckNull = True

End Function

Public Function CheckBlank() As Boolean
    
    CheckBlank = False
    If Text0 = "" Then CheckBlank = True

End Function

Public Function CheckSpace() As Boolean
    
    CheckSpace = False
    If Text0 = Chr(32) Then CheckSpace = True

End Function
Copy

Then for the Conditional Formatting rules, just:

Expression Is: CheckNull() = True
Expression Is: CheckBlank() = True
Expression Is: CheckSpace() = True

It didn't matter which order I put the Conditional Rules in, they all worked as expected

Thanks a lot for your help, Donald. Sorry for not answering faster. I was busy with something else.
CheckNull() and CheckBlank() work well, but CheckSpace() does not. Don't pass your time for this anymore. For me it is not absolutely necessary, but just "Nice to have".
Greetings
Rolf