Re: is pivoted phones view updateable?

From: NENASHI, Tegiri <tnmail42_at_gmail.com>
Date: Wed, 15 Nov 2006 01:44:58 +0100 (CET)
Message-ID: <Xns987BC9585DFE9asdgba@194.177.96.26>

"Vadim Tropashko" <vadimtro_invalid_at_yahoo.com> wrote in news:1163523276.819401.288540_at_m7g2000cwm.googlegroups.com:

> NENASHI, Tegiri wrote:

>> The view is not correct:  suppose (2) has not the FAX.  One goes to
>> lose (2) in the view oldcontactview.

>
> The view (2) is supposed to reflect the data in the table
>
> ID VOICE FAX
> 1 4150000000 4081111111
> 2 80012345672 6501234567
>
> which doesn't have NULLs. Perhaps this should be stated as an explicit
> constraint?

Pardon me but you did not understand well what I have wrote:

Suppose that the row with id = 2 of the newcontact table has not the fax number. You go to lose the personne whose id = 2 in the view oldcontactview. What you do in this situation ? Suppose you add more types of phone and the personne can have one or two or three or more phones ? What you do in this situation ?

>

>> The  PIVOT/UNPIVOT is not expressable in general in the relational
>> algebra because the algebra has not the NULL.  One has to extend the
>> algebra.  What is your extension ?

>
> UNPIVOT/PIVOT is expressable, however.

I think that you are rihgt that UNPIVOT does not suffer of the NULL problem.

>
> Regardless, the example in the beginning of the thread is even more
> simple (and NULL immune). Although, it seems to require a whole lot of
> algebraic manipulations to invert it.

I do not understand all the notation.

>
>
Received on Tue Nov 14 2006 - 18:44:58 CST