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Re: Counting propositions

From: Tony <andrewst_at_onetel.net.uk>
Date: 18 Jun 2004 12:17:47 -0700
Message-ID: <c0e3f26e.0406181117.4941b8f6@posting.google.com>


"x" <x-false_at_yahoo.com> wrote in message news:<40d2cceb$1_at_post.usenet.com>...
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>
> "Tony" <andrewst_at_onetel.net.uk> wrote in message
> news:c0e3f26e.0406180226.5b4153a0_at_posting.google.com...
>
> > > You see, there might be a relational database that has no named
> > > relation/relvar that (directly) assert employment.
> >
> > A badly designed, and probably un-normalised, database I would suggest
> > ;-)
>
> Well, you cannot always choose the design :-)

... in which case, maybe you can't get useful information from it.

> Why unnormalized ?

Because you apparently have no table in which emp_id is unique, and so nowhere for a fact about an employee to be stored once and only once.

>
>
> > > It works only when you count Emp_IDs, not the propositions employing
> Emp_IDs
> > > :-)
> >
> > No, it always works when you count propositions whose intention is to
> > state the existence of an employee. Of course it doesn't work if you
> > count propositions about project assignment or the employees' CD
> > collections etc.!
>
> In order to count propositions whose intention is to state the existence of
> an employee, you rely on Emp_IDs one-to-one corespondence with the
> employees, so you really count those Emp_IDs. :-)

You certainly can count emp_ids. Or you can count whole propositions, if you know that those propositions have a one-to-one correspondence.

> > But, for every table, "select count(*)" provides useful information -
> > provided you understand what the table means.
>
> I just showed you that you don't need to count the propositions for counting
> the employees. :-)
> You only need to count the Emp_IDs ... :-)

... the emp_ids in that table yes - which amounts to the same thing, by definition. It would be no good counting the emp_ids in a table that didn't have propositions about EVERY employee - e.g. if not all employees are assigned to projects, then counting the emp_ids in the assignment table would tell you how many employees are assigned to projects, not how many employees there are period. Received on Fri Jun 18 2004 - 14:17:47 CDT

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