Re: Too add a new table or not

Your boss is correct:-) There is nothing in relational theory that limits the number of fields in a table.

There are however some structures where the _relevance_ of some attributes depends on the value of a particular attribute. For example, in a table of 'Persons', a person of type='Teacher' may have a relevant attribute called 'salary', whereas salary will not be relevant for another one of type='Pupil'. For this type of person, 'grade' is relevant.

Some advocate creating different tables to hold the attributes 'salary' and 'grade', having a 1-1 relationship with the table Persons. The technique is called "subtyping" and is advocated mostly by Access developers. I am against it because 1-1 is not normalization, it's just the technical inability to use CHECK constraints in a particular RDBMS.

Conclusion: your boss is correct:-)

Radu

"Pavs" <pavle_sturma_at_hotmail.com> wrote in message news:692c44aa.0111052053.2bddc0ac_at_posting.google.com...
> I was wondering what the rule is when it comes to adding a new table
> to a data structure as oppossed to sticking with existing tables and
> shoving all the new attributes in the existing tables. (Assume that
> the data remains normalised)
>
> My boss with way more experience then myself argues that more can be
> done with less. "Why subject the database engine to more hits across
> multiple tables when you can stick to the one table" he says.
>
> Well whats the rule?
Received on Tue Nov 06 2001 - 08:06:49 CET