Re: So what's null then if it's not nothing?
From: FrankHamersley <FrankHamersleyZat_at_hotmail.com>
Date: Thu, 24 Nov 2005 12:28:46 GMT
Message-ID: <2mihf.2809$ea6.957_at_news-server.bigpond.net.au>
>
> I agree. They're not the same.
>
>
> Omitting the row sounds right. Using NULL is certainly wrong. The thing
> doesn't exist. Nor does <WhatYouDidLastNight/>. Using NULL for
> everything that doesn't exist would take up a considerable amount of
> storage space - like the size of the known universe and more.
>
> In the first example, yes.
>
>
> It should be represented by NULL. NULL is, after all, regardless of
> data type.
>
>
> Correct.
>
>
> Regards
> Mike.
Date: Thu, 24 Nov 2005 12:28:46 GMT
Message-ID: <2mihf.2809$ea6.957_at_news-server.bigpond.net.au>
michael_at_preece.net 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 >>>><1132350557.673092.92800_at_g49g2000cwa.googlegroups.com>) 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 >>table.
>
> 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