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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 21:50:32 +0100
Message-ID: <1cl9o1124gft5kobt0e9fsp06rlos9pvh1@4ax.com>


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

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. The Pick data model appears to accept this (unless the DB engine checks before inserting the data), as does XML.

Best, Hugo

-- 

(Remove _NO_ and _SPAM_ to get my e-mail address)
Received on Wed Nov 23 2005 - 14:50:32 CST

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