# Re: Limits

From: JOG <jog_at_cs.nott.ac.uk>

Date: Fri, 25 Jul 2008 14:58:38 -0700 (PDT)

Message-ID: <7a205ced-bd9c-47b9-8320-63200e13fed7@f63g2000hsf.googlegroups.com>

Date: Fri, 25 Jul 2008 14:58:38 -0700 (PDT)

Message-ID: <7a205ced-bd9c-47b9-8320-63200e13fed7@f63g2000hsf.googlegroups.com>

On Jul 25, 7:04 pm, Tegiri Nenashi <TegiriNena..._at_gmail.com> wrote:

*> On Jul 25, 7:30 am, JOG <j..._at_cs.nott.ac.uk> wrote:*

*>*

*> > As it is with ORDER BY I guess, which is supposed to spit out a linear*

*> > ordering where only a partial ordering may exist.*

*>*

*> Could you please be more specific? All SQL datatypes I know (well,*

*> those that I'm using -- string, number, date) are total orders. What*

*> partial ordered datatype do you have in mind?*

the tuple itself. For instance if we have relation: R := {w, x, y}

where the tuples are:

w := (a:1, b:1) x := (a:2, b:2) y := (a:3, b:2)

then "ordering by a" yields a total ordering over R: {(w, x), (w,y), (x,y)}

but "ordering by b" gives the partial ordering: {(w, x), (w,y)}

Regards, J. Received on Fri Jul 25 2008 - 16:58:38 CDT