Re: The Practical Benefits of the Relational Model
From: Mikito Harakiri <mikharakiri_at_yahoo.com>
Date: 5 Oct 2002 06:40:23 -0700
Message-ID: <bdf69bdf.0210050540.6dd309d7_at_posting.google.com>
Date: 5 Oct 2002 06:40:23 -0700
Message-ID: <bdf69bdf.0210050540.6dd309d7_at_posting.google.com>
> Therefore, the pairs of dual relational operations are:
> 1. Intersection is dual to Cartesian Product.
> 2. Union is dual to Naisetrac Product.
> 3. Selection is dual to Projection.
Correction:
Intersection = Cartesian Product * Selection Union = Naisetrac Product * Projection
Therefore:
- Intersection is dual to Union (as in the set theory;-)
- Cartesian Product is dual to Naisetrac Product
- Selection is dual to Projection