Re: Storing derived and derivable data

x wrote:
> "dawn" <dawnwolthuis_at_gmail.com> wrote in message
> news:1145717081.072600.109970_at_i39g2000cwa.googlegroups.com...
>
>
> > I am referring to any notation anywhere, perhaps in a conceptual or
> > logical data model, for example. While there are terms to distinguish
> > between a base table and a materialized view, for example, I have not
> > found the right terms to distingish a derived materialized attribute
> > from on that is not derived from values in the database. I would like
> > to write about such attributes and am not finding terminology or
> > notation to do so.
>
> I think you talk about using expressions like values.
> A cross of functional calculus and predicate calculus or predicate calculus
> with equality.

I'm talking about taking a single derived value or an entire column of derived values and adding those values into a stored column. I am not talking about taking a snapshot of an entire table or view. For example, if we have a base relation

Students {Name, Major}

and we have a derived attribute (stored procedures, udf...) for the GPA, then we add a column to our base relation to get

Student {Name, Major, GPA}

We then either need the DBMS (as in the case of Sybase, it appears), a trigger, or some other process to keep the GPA in synch with the stored data from which it is derived. The purpose of this would be performance in read-only situations.

Did that clarify? Thanks. --dawn Received on Fri Apr 28 2006 - 17:24:40 CEST