Re: is pivoted phones view updateable?

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?

> 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.

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. Received on Tue Nov 14 2006 - 17:54:36 CET