Re: View updating in practice?

Jens Lechtenbörger wrote:

> I wonder if anybody uses view updates in practice and if so what kind
> of updates on what kind of views.

        It's too much of a trouble in SQL. I'm looking forward to use them extensively in any TTM-compliant D, such as Alphora Dataphor's D4.

        Basically the idea is to user derived relations to be able to change the physical, logical and (or) users' schemas without having to change most programs nor invalidate most of users' knowledge of the database. AKA data independence.

> Personally, I believe that view updates are dangerous in most
> situations as users cannot understand what is going on. To give two
> simple examples: In case of deletions from projections, users delete
> tuples they do not know completely. In case of insertions into
> joins, users do not know whether they are actually inserting into
> both operand relations or whether there was a dangling tuple in any
> of the operand relations that gets "absorbed" by the newly inserted
> tuple. It is easy to see that users will not be able to undo their
> view updates (such that the old _database_ state is reached) using
> further view updates in the above situations. If a was a user of
> such a database I would be very irritated.

        Now suppose you are a *relational* database user. When you try to insert back data, you would get a message stating which constraints you violated. The system could even do a limited natural language translation of the constraints, like "attributes X and Y in relation A have no defaults". Then providing this additional information would be trivial.

> I wrote a paper on this topic for ICDT'03. (Take a look at
> http://dbms.uni-muenster.de/publications/downloads/view-updates.pdf
> if you are interested in the details.) Unfortunately, the paper got
> rejected, but I'm not convinced by the reviewers' critique ;) Now, I
> would like to know what people do in practice. My questions are as
> follows:

        Would you inform us the critique?

> 1. Do you use view updates? What is the scenario?

        No.

> 2. If you do _not_
> use view updates, did you at least think about using them? If so,
> what was the application scenario and why did you not implement it
> (e.g., no support by DBMS or too complicated for users)?

        SQL support is insane.

> 3. Does
> anybody use SQL:1999 INSTEAD triggers to implement view updates?

        I hate triggers…

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