Re: Can relational alegbra perform bulk operations?

From: Vadim Tropashko <>
Date: Tue, 29 Sep 2009 21:10:40 -0700 (PDT)
Message-ID: <>

On Sep 29, 3:14 pm, paul c <> wrote:
> When it comes to relational algebra, I doubt if there are any advanced
> books

Indeed. I would challenge the term "relational algebra". Consider how relational division is introduced; a typical textbook goes like this:

"Consider the two relations with disjoint headers ... Their cartesian product is ... Now imagine we want an operation that is inverse to cartesian product..."

The discussion often revolves around concrete examples (PilotsSkill/ Hangars, Certifications/Requirements, etc). This is essentially the level of elementary second grade math textbook depicting how to arrange items into rows and columns, and then how to calculate the number of rows when one knows the total number of things. It is arithmentics, not algebra.

An algebraic question maybe if division is residuated operation (it is not); then it is mysterious why relational division fits the role of inverse to join. Perhaps, this fact hints the existence of many division-like operations? Received on Tue Sep 29 2009 - 23:10:40 CDT

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