Re: Multivariate relation (Was topological databases)

On Tuesday, January 27, 2015 at 10:01:12 PM UTC-8, Derek Asirvadem wrote:
>
> SELECT /column_name_list/
> ____FROM { /table/ | /view/ | /derived_table/ }
> ____ORDER BY { /column_name/ | /column_no } [, { /column_name/ | /column_no } ] ...

This syntax is wrong, because "order by" clause allows arbitrary expressions, e.g.

select * from employees order by salary+1

The "1" there, is it a column number? What column does it refer to? I understand that it is possible that the original SQL standard might not have expressions. Still, in normal programming language as soon as one feature is introduced, other is deprecated. What are those column numbers are for, to save a user few keystrokes? In modern world with auto completion?

> Last question. Why then, call the unnamed perspective "multi-variate relations" ?

Consider multivariate polynomial system

$latex x^2-3 x+2 = 0 $
$latex y-1 = 0 $
$latex z-1 = 0 $

it has 2 zeroes:

x=1, y=1, z=1
x=2, y=1, z=1

In other words, we have relation

x y z
- - -
1 1 1
2 1 1   Received on Wed Jan 28 2015 - 18:51:54 CET