Re: the idea of unique primary keys to be a solution that hasoutl ived its usefulness?

----- Original Message -----
From: "DeLong, Eric" <EDeLong@xxxxxxxxxxxxxxx>
To: "'RPG programming on the AS400 / iSeries'" <rpg400-l@xxxxxxxxxxxx>
Sent: Monday, November 17, 2003 10:24 PM
Subject: RE: the idea of unique primary keys to be a solution that hasoutl
ived its usefulness?


> Unique primary keys are not what most of us use on the iSeries.  We use
> unique compound keys, where the combination of many factors (keys) work
> together to define a unique row.  Unique primary keys are a single field
> that describes a unique row.  These are commonly implemented as UUIDs, or
> possibly as auto-incrementing value for such things as order number and
> whatnot...

Who says so? Primary keys can be compound.

>From 'A Guide to the SQL Standard' (C.J. Date / Hugh Darwen):

In SQL, a candidate key definition takes the form
    { PRIMARY KEY | UNIQUE } ( column-commalist ).
For a given base table, at most one candidate key definition can specify
PRIMARY KEY.

Joep Beckeringh