Re: OOP real life example (was Re: Why is MySQL more

On Mon, 2002-08-12 at 11:52, Curt Sampson wrote:
> On Sun, 11 Aug 2002, Don Baccus wrote:
>
> > Obviously it would require extending SQL, but since you in part argue
> > that SQL sucks in regard to the relational model this shouldn't matter,
> > right?
>
> Well, if we're going to go so far as to get rid of SQL, we can go all
> the way with the D&D thing, and VIEWs will no longer be syntatic sugar
> because views and tables will be the same thing. (I'll leave you how
> specify physical storage as an exercise for the reader. :-))
>
> But anyway, I have no particularly huge objection to syntatic sugar
> alone. I do have objections to it when it's not saving much typing. (It
> is in this case, but that could be fixed with better automatic support
> of view updates.)
>
> But my real objection is when it makes things more confusing, rather
> than less, which I think is definitely happening here.

What makes things more confusing is poor understanding of a feature, not
the feature itself.

> I've never
> seen a rigourous explanation of our model of table inheritance,
> nor any model that was more obviously correct than another. And
> the parallel drawn with inheritance in OO languages is a false
> parallel that adds to the confusion.

Are you saying that inheritance in SQL is something fundamentally
different than inheritance in OO languages ?

> (For example, the distinction
> between types and instances of types is critical in OO theory. What are
> the TI equivalants of this?)

If by TI you mean type instance then the equivalent of of an instance is
a relation (i.e. one row in an (inherited) table).

> All this is borne out by the regular questions one sees about
> inheritance in the mailing lists. I'll admit a good part of it is
> due to the broken implementation of inheritance, but all of the
> problems I've ever seen are easily solved with very simple relational
> solutions.

All _simple_ inheritance problems are easily solved by simple relational
solutions. The general problem of much more typing and debugging, less
clues for optimiser etc. are not solved by _simple_ relational
solutions.

> Maybe the inheritance thing is causing people to turn off the relational
> parts of their brain or something.

Of maybe people are diversifying, using inheritance for is-a
relationships and relational model for has-a relationships.

---------------
Hannu