From: Todd Benson <caduceass@...>
Date: 2008-04-13T09:14:32+09:00
Subject: Re: [OT] Re: How to check record duplication before saving?

On Sat, Apr 12, 2008 at 3:55 PM, ara.t.howard <ara.t.howard@gmail.com> wrote:
>
>  On Apr 12, 2008, at 10:34 AM, Todd Benson wrote:
>
> >
> > In rails, I should point out I _have_ to use the integer ID for my
> > primary key, which irks me to no end because it goes against
> > everything I know about set theory.  That whining aside, I might try
> > to fix it, but the underlying rails code is intimidating.
> >
>
>  no db actually deals with sets - try to do a query and get the results back
> in different order each time.  in practice they are *ordered* tuples of key
> value pairs and every db i've used is written with this implicit
> understanding.  having an id is no different that having an 'updated_at'
> field - it simply provides a total ordering which is arbitrary.  fighting
> the id is just swimming upstream to nowhere - i know as i did it for a long
> time.  ;-)
>
>  a @ http://codeforpeople.com/

I understand that, for example, postgresql and mysql have labeled all
things with an integer.  But, in the table itself, umm, doesn't make
much sense...

create table my_set (
  id int not null primary key,
  a int,
  b int,
);

insert into my_set values (1, 1, 1);

insert into my_set values (2, 1, 1);

It gets even worse with built in functions like auto_increment, where
you've tossed all identity of the tuple to the wind (think of moving
such a table to another db).

I'm still a firm believer in using logical primary keys instead of
arbitrary ones anyway, even if it takes a little more effort, but I'm
willing to listen to other ways :-)

Todd