When I first started programming for DBMS I thought so too. After ten years in the paradigm, I use the distinction all the time.

Null means "I haven't touched it and don't know the value", while empty string means "I have deliberately said that it has an empty value".

The alternative is to add a flag to every field that would otherwise be nullable that tells you whether the field is truly empty or simply unknown. Then you have to maintain the separate flags, and you are making the null versus deliberately empty distinction manually.

----- Original Message -----
From: Jonathan Neve
To: firebird-support@yahoogroups.com
Sent: Tuesday, March 16, 2004 3:08 AM
Subject: Re: [firebird-support] Re: seems bug : Field accepts NULL Values (empty string) even if it is defined w


Alexander V.Nevsky wrote:

>--- In firebird-support@yahoogroups.com, Jonathan Neve <jonathan@m...>
>wrote:
>
>
>>Martijn Tonies wrote:
>>
>>
>>
>>>You're answering your own question: '' (empty string) is NOT NULL.
>>>NULL is NULL (empty). An empty string is a value. NULL is a state,
>>>so is "NOT NULL".
>>>
>>>
>>>
>>IMHO, this unique feature could nearly be considered a bug...
>>
>>
>
> In SQL standard? ;)
>
>
Absolutely! A bug in that it defines a useless distinction that would
forever be a nuisance for every database developer! :-)

Jonathan Neve.


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