Re: theoretical question on the RDBMS

Steve Kass <skass_at_drew.edu> wrote in message news:<3D5A4AA0.27A3623A_at_drew.edu>...
> I don't see where files and devices say anything about independence,
> and I suspect Paul is right that insofar as the theory talks about
> independence, it almost has to mean something logical, not physical.

I've just been reading a different but related thread ("normalization question") where you were wondering about data complexity and for example separating out a column which is usually NULL into a different table to save space. For some reason Google isn't letting me reply to that (too old?) but it's kind of relevant here.

I think perhaps (guess who's been reading the dbdebunk website) this is something that should be done at the physical, not logical level. i.e. behind the scenes the database could implement "sparse" columns in a separate "file" for performance reasons but at the logical (SQL) level it should be in the same table.

It seems to me perhaps there are two levels to being a DBA, one which is purely concerned with the logical level: SQL, data integrity, etc. where performance is irrelevant, and the other at the physical level, where decisions about indexing, table-to-file mappings etc. are made. I think perhaps current DBMSs are lacking in flexibility for the second (physical) level and tend to mix the two together in a way that can be confusing.

Paul. Received on Thu Aug 15 2002 - 11:24:11 CEST