Re: is pivoted phones view updateable?
Date: Wed, 15 Nov 2006 01:44:58 +0100 (CET)
Message-ID: <Xns987BC9585DFE9asdgba_at_194.177.96.26>
"Vadim Tropashko" <vadimtro_invalid_at_yahoo.com> wrote in
news:1163523276.819401.288540_at_m7g2000cwm.googlegroups.com:
>> 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 Wed Nov 15 2006 - 01:44:58 CET