# Re: Normalisation

Date: Tue, 5 Jul 2005 22:58:34 +0200

Message-ID: <MPG.1d3512e03d3a41939896e1_at_news.ntnu.no>

In article <PwBye.138032$Nn7.7012386_at_phobos.telenet-ops.be>,
jan.hidders_at_REMOVETHIS.pandora.be says...

> > How does a set domain (e.g. the domain of sets of integers) violate

*> > this? For definiteness, let's associate the normal set operations with
**> > it---union, intersection, subset, cardinality and so on.
**>
**> By itself it doesn't. Until you start introducing operations that treat
**> it as non-atomic. Then it does.
*

Does the common substring operation treat a string as non-atomic?

*> > How does that help with normalisation?
**>
*

> Since it defines atomicity it tells you when you are in 1NF or not. Just

*> to be clear on this, I regard this discussion separate from the question
**> whether you actually *should* be in 1NF or not.
*

> > And how can you say a priori that

*> > a relvar with a set-valued attribute is not in 1NF, if that depends on
**> > the operators of a particular DBMS?
**>
**> You cannot.
*

Yet you did say "Another option is to treat the field as a set-valued field (since it apparently can contain 0 or 1 values) which means that you are not in 1NF and should first normalize such that you are."

-- JonReceived on Tue Jul 05 2005 - 22:58:34 CEST