Karl Schendel wrote:
On Mar 3, 2021, at 11:55 AM, Allan Biggs <allanb4@iname.com> wrote:
Also sent to the OpenROAD group
I have spent the day wishing that I could update a view.
You can update a simple view that is just select columns from a table, and
I think a where clause is allowed.
The Standard allows updating a more general view, with a whole slew
of rules and regulations about what you can and can't update; but Ingres
has never bothered to implement it.
What Karl said. And if the view was created WITH CHECK OPTION you can
update it only in such a way that a successful update doesn't cause the
updated row(s) to disappear from the view.
The rules are much the same as for an updateable cursor.
Intererestingly not only can you update views, Ingres allows you to
define rules that fire when you you update a view just like rules on
a base table. I don't think that ability is mentioned in the
documentation but it is correct behaviour and it works. (Just don't
ask me to look after any system where you do that to make magical
things to happen.)
Incidentally, in 2013 Chris Date wrote an entire book (largely
unhindered by any thoughts of SQL): View Updating and Relational
Theory, ISBN 978-1-449-35784-9. I see the bookmark in my copy is well
over a quarter of the way through it...
Roy
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