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Re: Counting propositions

From: Tony <andrewst_at_onetel.net.uk>
Date: 18 Jun 2004 03:26:46 -0700
Message-ID: <c0e3f26e.0406180226.5b4153a0@posting.google.com>


"x" <x-false_at_yahoo.com> wrote in message news:<40d29127$1_at_post.usenet.com>...
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> "Tony" <andrewst_at_onetel.net.uk> wrote in message
> news:c0e3f26e.0406171213.73e101f7_at_posting.google.com...
>
> > > You see, there are propositions that assert the employment and
> propositions
> > > that assert other things about the employee.
> >
> > Yes - like a table of employee_salary_history may assert 7 facts about
> > 1 employee. But I know that, because an employee is identified by
> > Emp_id (or whatever), and this table of propositions is not.
>
> Funny that you mentioned Emp_id. :-)
>
> 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 ;-)

> Like:
>
> involved_in(Emp_id, Proj_id)
> manage(Emp_id, Proj_id)

...in which case "select count(*) from involved_in" would tell us how many "employee/project involvements" we have, not how many employees (or projects) we have - I am assuming you intented (emp_id, proj_id) to be the key.

> > > Not true. There might be more propositions per employee (without
> > > duplicates).
> >
> > Not in the table of propositions that has Emp_ID as the key there
> > can't be.
>
> It is possible to have no such table or serveral overlapping tables.
>
> > > Why do you insist in counting the propositions, for counting the
> employees
> > > then ?
> >
> > Because it works? ;-)
>
> 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.!

But, for every table, "select count(*)" provides useful information - provided you understand what the table means.

I am not at all sure what point it is you are labouring to make here: of course "select count(*) from tableX" tells you nothing useful unless you understand the meaning of the propositions tableX contains - in which case, the database is completely useless to you, period. Received on Fri Jun 18 2004 - 05:26:46 CDT

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