Re: A Normalization Question
Date: Fri, 09 Jul 2004 10:29:57 -0700
Message-ID: <40EED615.736C_at_assist.org>
Neo wrote:
> Because the three strings each represent the same thing, the string
> 'brown', it is redundant. To create an update anomaly, we need to
> perform an update. This is unusual with strings, because strings
> typically don't change and if they change we consider them to be a
> completely different string.
But facts change, and that's the entire point.
With your methodology, update anomalies easily result. Given the schema I provided earlier:
create table house_color (
Suppose the manufacturer of the paint used for the
exterior renamed all their paint colors, and "brown"
is now called "St. Tropez Tan." If you simply change
the one instance of "brown" in your schema you have,
customer_id numeric(5) not null,
exterior_color varchar(10) not null,
interior_color varchar(10) not null,
trim_color varchar(10) not null,
primary key (customer_id)
)
Larry Coon
University of California
Received on Fri Jul 09 2004 - 19:29:57 CEST