Re: Examples of SQL anomalies?
From: Marshall <marshall.spight_at_gmail.com>
Date: Sat, 5 Jul 2008 09:13:56 -0700 (PDT)
Message-ID: <5f65dab7-799f-4a5e-853d-21c4c53ad227_at_79g2000hsk.googlegroups.com>
Date: Sat, 5 Jul 2008 09:13:56 -0700 (PDT)
Message-ID: <5f65dab7-799f-4a5e-853d-21c4c53ad227_at_79g2000hsk.googlegroups.com>
On Jul 5, 5:55 am, goanna <spamt..._at_crayne.org> wrote:
> Marshall <marshall.spi..._at_gmail.com> writes:
> > What can be meaningfully asked is determined by the schema.
>
> Close. What can be meaningfully asked is determined by
> the meaning of the schema.
The schema is syntactic. What questions can be syntactically constructed (that is, asked) is determined by the schema. What the schema means is semantic. What a syntactically correct query means is determined by the external predicates of the schema.
> In the case of nullable attributes, this must be
> specified, not guessed.
In all cases, meaning is in the head of the programmer, and not in the dbms.
Marshall Received on Sat Jul 05 2008 - 18:13:56 CEST