Re: Functional Dependencies > Uniqueness Constraints
From: Jan Hidders <hidders_at_gmail.com>
Date: 30 Aug 2006 04:18:23 -0700
Message-ID: <1156936703.543074.207880_at_m73g2000cwd.googlegroups.com>
> To sum up: A good RDBMS should be able to infer FDs from keys /
> uniqueness constraints (and inclusion dependencies), and reason about
> them; in particular, to infer FDs (and thus keys) for arbitrary relation
> expressions, e.g. in order to perform semantic optimisation.
Date: 30 Aug 2006 04:18:23 -0700
Message-ID: <1156936703.543074.207880_at_m73g2000cwd.googlegroups.com>
Jon Heggland wrote:
>
> To sum up: A good RDBMS should be able to infer FDs from keys /
> uniqueness constraints (and inclusion dependencies), and reason about
> them; in particular, to infer FDs (and thus keys) for arbitrary relation
> expressions, e.g. in order to perform semantic optimisation.
On the other hand, in general the implication problem for INDs and FDs is undecidable.
- Jan Hidders