Re: atomic

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Fri, 02 Nov 2007 12:48:23 -0300
Message-ID: <472b46cb$0$14877$9a566e8b@news.aliant.net>

paul c wrote:

> paul c wrote:
>

>> Roy Hann wrote:
>>
>>> "paul c" <toledobythesea_at_ooyah.ac> wrote in message 
>>> news:08HWi.167005$Da.137917_at_pd7urf1no...
>>>
>>>> If I may dodge the ordering question for now and continue with my 
>>>> casual graphics, how could a relation like the following be useful? 
>>>> (assuming one pizza per order and ignoring pizza size)
>>>>
>>>> PizzasOrdered:
>>>>
>>>> Order {Toppings}
>>>> _____ __________
>>>>
>>>> 1     {Tomato, Sausage, Cheese}
>>>> 1     {}
>>>
>>>
>>> If the predicate is something like "The kitchen is currently cooking 
>>> <order> pizzas with <toppings>", where <order> is a count.  (i.e. 
>>> someone has ordered just a crust--my son would, and someone else has 
>>> ordered a proper pizza.)  I could no doubt invent other possible 
>>> interpretations.  My question is, what predicate did you intend me to 
>>> use when answering your question?
>>
>> I think your predicate is fine.  ...

>
> Sorry, let me take that first sentence back as I didn't notice at first
> that you are called <order> a count. So I guess I should say the
> predicate I had in mind was "the pizza for order <order> has the set of
> toppings <toppings>.
>
> I still wonder why one would want both tuples to apply to the same pizza.

With your predicate, I doubt one would, which is why one would declare a candidate key that would reject the relation. Received on Fri Nov 02 2007 - 10:48:23 CDT