Re: 3vl 2vl and NULL

From: Frank Hamersley <terabitemightbe_at_bigpond.com>
Date: Sun, 08 Jan 2006 01:42:18 GMT
Message-ID: <_5_vf.209801$V7.138519@news-server.bigpond.net.au>

dawn wrote:
> Frank Hamersley wrote:
>

>>dawn wrote:
>>
>>>Frank Hamersley wrote:
>>>
>>[....]
>>
>>>If the data model visualized on the screen has one instance of an ID
>>>and the SQL view backing that screen has many instances of this same ID
>>>value, then the data models are different.
>>
>>Are we talking about the model or manifestations of it (instances)?

>
> We are talking about the logical model itself, but perhaps using that
> term differently. A logical model that is in first normal form is
> different from a model of that same data that is not. They are not the
> same model simply because they model the same thing. Trees, networks,
> and relations might all model the same data, but they are not the same
> model. The model associated with a screen of data is not typically a
> no-repeating-groups relation as required if it were to be output
> directly from a SQL-92 view.

You are presuming that visibility of all the data on the "screen" is mandated. Personally I have no such hang-ups*.

• see below.

>>[..]
>>
>>>>I think you have expressed most clearly the core of the problem
>>>>troubling you.  It seems you can't accommodate the SQL outcomes because
>>>>it doesn't have a "shape" that you are comfortable with.
>>>
>>>I'm actually quite comfortable with it, but I don't see an advantage to
>>>using it to the extreme typically employed with SQL-DBMS's.
>>
>>I'm missing something - what is the "extreme" bit?

>
> If there really is a reason to have data in base relations with no
> repeating groups, surely that requirement goes away with relations that
> are logical views of the data. SQL permits views not to be in 2NF,
> 3NF, BCNF, 4NF, ... but took this notion of no repeating groups to the
> extreme and requires it even in logical views of the data.

As DC said I don't see any reason for exchange of information from the DBMS to the Screen App to be exclusively 1NF in the strictest sense. I suspect you feel that "softness" weakens the process more so than the 2VL/MV no translation mantra holds.

I disagree - there are measurable gains to be had in adopting the RM for the storage engine that, IMO, outweighs any perceived cost of developing and maintaining a dialect to transfer information from it to a application. In my view the 2VL/MV actually allows, nay encourages, that "softness" to find its way into the repository, which in the wrong hands is a Bad Thing tm.

>>>>That is
>>>>something for you to deal with although I suspect you are not alone.
>>>>The vast number of cursor happy application developers are a testament
>>>>to that.
>>>
>>>I like set manipulations, but have no need to block other types of
>>>access where useful.
>>
>>So do I, and I rarely find other types of access useful.  Admittedly
>>there are some and I will freely confess to the occasional use of a
>>cursor as a last resort.
>>
>>
>>>>Good luck on the journey Grasshopper!
>>>
>>>Much appreciated Master.
>>
>>Thats a good first step :-)

>
> I've worked with men my entire career.

How do you know I was not cross-dressed at the time of writing?

BTW I don't know if google will explain the various antipodean male rituals but be assured that is a certainty at some stage - often attended shortly thereafter by copious amounts of fermented fluids!

[..]

Cheers Frank. Received on Sat Jan 07 2006 - 19:42:18 CST