Re: SQL Existence Check

["Leif Svalgaard" <leif@xxxxxxxx>]

From: Vernon Hamberg <vhamberg@attbi.com>

> OK, got ya. I'm just looking this up to learn a little more. Thanks for the
> eye-opener.
> This looks like physical layer implementation. What would have to happen
> for a database to be relational at this level? Is not the 400 relational at
> the user level?

there is also the aspect of simple hype. I sometimes hear the
AS/400 being described as object-oriented at the OS-level.

If you access the database with SQL I guess that you can say
that the DB is relational at the user level, except of course that
most users never see or use the SQL. What is a user?
The data-entry clerk?, the programmer?, the system programmer?

My answer would be that IBM has built a relational front-end
to an ISAM database. Other implementations that I know of
may be closer to a relational database at the low level, e.g.
one where each attribute (column, field, ...) is stored in its
own separate file.

Joe's point is important too. SQL (and the relational model)
is very inefficient for sequential access. Try to walk through
all records where the key is greater than a certain value. Now,
SQL "bigots" may say that that is a silly thing to do, and I don't
want to get into that discussion.