Re: database design method
Date: Mon, 18 Nov 2002 09:35:45 +0200
Message-ID: <3DD89851.71B3CCFC_at_atbusiness.com>
Jan,
The only question I know how to ask is the following:
>>> Suppose I have a relation
> > - I would suppose that the id's could be generated
Surely if that same view (that generates - perhaps abstract -
identifiers) is queried many times, it represents each time
the values of the execution at that point of time. So if
I query it twice it makes no difference whether the
identifiers are the same or not, or what the result
of the query is.
So if I say
select * from cust_class
and get the answer {(1,1),(1,2),(2,3)}
and re-execute it after 10 minutes
and get the answer {(1,1),(2,2),(2,3)}
that would be perfectly correct because
>>>
>>> Bought(customer, product)
>>>
>>> and I want as the result a relation
>>>
>>> Cust_class(class_id, customer)
>>>
>>> that groups the customers into classes that have bought the same set of
>>> prodcucts and gives them a new identifier.
> >each time the query was executed - what's the problem?
>
> If it is executed a lot you may run out of them.
it would just be the result of the query
and that's it.
regards,
Lauri Pietarinen
Received on Mon Nov 18 2002 - 08:35:45 CET