Re: Unable to use VIEWS (Ok button remains shaded)

On Thu, Sep 16, 2010 at 10:00 PM, Mladen Gogala
<mladen.gogala@vmsinfo.com> wrote:
> I always wandered why would anybody want to update a view? View is, by
> definition, a stored query which is executed frequently enough to be given
> its own first name, middle name and a family name.  If the view is being
> updated, the middle name is  F, just as in the case of Bucky Dent. I don't
> see  any database design pattern which would necessitate  updating a view.
> That is a perversion, not unlike putting ketchup on a hot dog.

See C.J. Date's "SQL and Relational Theory", a good read. Page 195,
"SQL and Views: Update Operations" talks about this. Quote:

>>  The Principle of Interchangeability implies that views must be
>>  updatable (i.e., assignable to) ... [snip] ... updates on base relvars can
>>  always fail on integrity constraint violations—and the same is true
>>  for updates on views. In other words, it isn’t that some views are
>>  inherently nonupdatable, but rather that some updates on some
>>  views will fail on integrity constraint violations (i.e., violations of
>>   The Golden Rule).

On page 197 Date gives an excerpt from SQL99 that defines when a view
is updatable, see page 269 of SQL99 here:
http://www.cs.pdx.edu/~len/sql1999.pdf

Josh