Oracle FAQ Your Portal to the Oracle Knowledge Grid
HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US
 

Home -> Community -> Usenet -> comp.databases.theory -> Re: So what's null then if it's not nothing?

Re: So what's null then if it's not nothing?

From: Hugo Kornelis <hugo_at_pe_NO_rFact.in_SPAM_fo>
Date: Wed, 23 Nov 2005 00:29:31 +0100
Message-ID: <n9a7o19tgpqndqkdkpa9s6pq71d8p2jcu4@4ax.com>


On Tue, 22 Nov 2005 07:01:43 -0600, N. Shamsundar wrote:

>Hugo Kornelis wrote:
>> On Thu, 17 Nov 2005 10:27:55 -0600, N. Shamsundar wrote:
>>
>> (sniip)
>>
>>>Try this: every logical expression has three possible values, not two as
>>>in languages such as C, Pascal, Fortran, etc. They are, as you seem to
>>>have recognized, "TRUE", "FALSE" and "UNKNOWN" (named "NULL" in SQL).
>>
>>
>> Hi N.,
>>
>> This is incorrect. "UNKNOWN" is not named "NULL" in SQL. See my long
>> post to Mike.
>
>Which one?

Hi N.,

Here's the message-ID: <ro4qn1hmsgulnjfvtbp09834mh1qc546v3_at_4ax.com>

>>>If
>>>you keep this in mind and refrain from using other notions such as the
>>>NULL in C (a pointer value that you may not dereference, etc.)
>>
>>
>> Since SQL's Null is a marker or the absence of a value and C's NULL is a
>> pointer to nothing, they are in fact more similar than you seem to
>> suggest here.
>>
>> Best, Hugo
>
>This short piece of C will illustrate that nulls in C are different from
> SQL's null.

(snip)

Sorry for the confusion - I never intended to imply that they are the same, just that there are parallels in the underlying concepts.

SQL Null: marks the absence of a value - i.e. it says: "nothing here". C Null: points to nothing - i.e. it says: "nothing there".

Best, Hugo

-- 

(Remove _NO_ and _SPAM_ to get my e-mail address)
Received on Tue Nov 22 2005 - 17:29:31 CST

Original text of this message

HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US