Re: In an RDBMS, what does "Data" mean?
Date: Tue, 15 Jun 2004 08:39:09 -0400
Message-ID: <TPSdnXgqT7AJcFPdRVn-jA_at_comcast.com>
"Tony" <andrewst_at_onetel.net.uk> wrote in message
news:c0e3f26e.0406150138.d389afd_at_posting.google.com...
> "Anthony W. Youngman" <wol_at_thewolery.demon.co.uk> wrote in message
news:<qZztNxCLLizAFwnY_at_thewolery.demon.co.uk>...
> False. A relational database contains a lot of metatdata:
> primary/unique keys, foreign keys, other constraints. All of these
> are available to the RDBMS for optimisation purposes. To take your
> invoice example, the RDBMS "knows" that a given invoice has 14 invoice
> lines just as surely as Pick does.
Excellent, excellent point. So many people fail to recognize this feature of an RDBMS.
When I built a "data mart" in Oracle as a star schema, I included all the
primary and foreign key constraints, even though it slowed down loading.
The advantage came when I went to copy the star into Cognos (Impromptu or
Power Play, I forget)
Both Cognos and the Oracle optimizer recognized my star schema for what it
was, and made appropriate use of that fact.
Received on Tue Jun 15 2004 - 14:39:09 CEST