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

From: FrankHamersley <>
Date: Thu, 24 Nov 2005 12:28:46 GMT
Message-ID: <2mihf.2809$> wrote:
> Hugo Kornelis wrote:

>>On Wed, 23 Nov 2005 01:09:56 GMT, Frank Hamersley wrote:
>>>Hugo Kornelis wrote:
>>>>Mind you, I don't *KNOW* it can, since I know nothing about Pick. But
>>>>the description of Pick's data structure that DonR wrote (message-ID
>>>><>) reminds me very
>>>>strongly of XML. And in XML, it's easy to simply remove a "field" from a
>>>>"row": in "<Person><Name>Hugo Kornelis</Name></Person>", there are no
>>>>tags for birthdate, which clearly indicates that the value for my
>>>>birthdate is absent in this piece of data.
>>>Is "<Person><Name>Hugo Kornelis</Name></Person>" the same as
>>>"<Person><Name>Hugo Kornelis</Name><Birthday></Birthday></Person>"?
>>Hi Frank,
>>I don't think so.

> I agree. They're not the same.
>>I the first XML string, there is no Birthday attribute
>>for me. It's missing. In SQL, this would be represented by NULL in the
>>table, or my omitting the row if the birthday were stored in a seperate

> Omitting the row sounds right. Using NULL is certainly wrong. The thing
> doesn't exist. Nor does <WhatYouDidLastNight/>. Using NULL for
> everything that doesn't exist would take up a considerable amount of
> storage space - like the size of the known universe and more.

Everything after the 1st sentence of the preceding para itself is worthy of NULL. Nuff said!

>>In Pick, this would (as I understand it) be stored by omitting
>>the cell for Birthday.

> In the first example, yes.
>>The second XML string lists a blank birthday for me. That can't be
>>stored in SQL, as it's strong typing prevents a date from being blank.

> It should be represented by NULL. NULL is, after all, regardless of
> data type.
>>The Pick data model appears to accept this (unless the DB engine checks
>>before inserting the data), as does XML.

> Correct.
>>Best, Hugo

> Regards
> Mike.

Where it gets more interesting is if you throw the following at the RM (Pick will have no trouble AFAICT).

<People><Person><Name>Hugo Kornelis</Name></Person> <Person><Name>Frank

Cheers, Frank. Received on Thu Nov 24 2005 - 13:28:46 CET

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