Re: Counting propositions
Date: Mon, 21 Jun 2004 18:54:02 +0300
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"Tony" <andrewst_at_onetel.net.uk> wrote in message
> > > > 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.
If the boss tells you to get that information, you cannot answer *maybe*. If the relation that assert employment is not a named relation, you can name 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.
So what. Who said there must be such a table in a normalized design. You don't store employees. Remember ? You only talk about them. :-)
> You certainly can count emp_ids. Or you can count whole propositions, > if you know that those propositions have a one-to-one correspondence.
If I can count the emp_ids, why bother counting the propositions ?
> > > 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
> > 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.
I just count the Emp_IDs in the active domain for Emp_IDs. This ensure that I count EVERY employee :-)
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