Ann W. Harrison wrote:

> Yes. The original design decision not to mix ascending and
> descending keys in an index was driven by testing that showed
> that to return the entire record set, sorted, it was
> significantly faster to fetch the records in storage order
> and sort them. Since then, people who learn SQL application
> programming on other systems have developed a style where the
> most important feature is not the time to get the whole
> record set, but the time to get the first record. [...]

It is not so much (or not only) where people learn programming
style, but also the intended purpose of a given query.

Applications using Relational database technology are more
diverse than when the theories (and mature products like IB/FB)
were developed. The application requirements and the theories
are not always an ideal fit - but is is often preferable (to
the application developer) to try and force a fit rather than
to change products or add more products to a solution.

Exactly how you optimise any product to give the best of both
worlds remains an interesting question, both application
developers and the supporting products continue to adapt.

--
Geoff Worboys
Telesis Computing