Re: Distributed foreign keys (was Re: Category Types)
Date: Fri, 20 Jun 2003 11:34:14 -0700
Message-ID: <vzIIa.5$yt4.164_at_news.oracle.com>
"Paul Vernon" <paul.vernon_at_ukk.ibmm.comm> wrote in message
news:bcukop$29r4$1_at_gazette.almaden.ibm.com...
> Thanks. Now make that a monthly payment to me, so making my annual Salary
$0,
> which (it could be argued) is different than not having a salary at all.
>
> On the other hand, if you constrain all payments to be greater than $0,
then a
> Salary of $0 could be defined as being equivalent to not having a salary,
but
> then why have two ways of representing the same thing?
You introduced monthly payments, which lowers the level of "annual salary" abstraction. Then, "annual salary" is an aggregate sum of monthly payments, and NOT_SALARIED relation is just a view
select name from EMP
minus
select recipient as name from PAYCHECKS
group by recipient
One, or the other way NOT_SALARIED is redundant! Received on Fri Jun 20 2003 - 20:34:14 CEST