Re: 4 the FAQ: Are Commercial DBMS Truly Relational?

"Marshall Spight" <mspight_at_dnai.com> wrote in message news:bVT9d.361333$Fg5.257522_at_attbi_s53...

> NULLs certainly suck in a lot of ways. In the context of the
> semi-mainstream definition of 1NF (what Alfredo would call
> the broken definition) NULLs are hard to get away from, because
> you need some operation like LEFT OUTER JOIN. If you
> have Relation Valued Attributes (RVAs) and some GROUP BY
> operator, though, you don't need NULLs even for OUTER
> JOINs.

However, note that the result of an outer join is not necessarily a relation, even if both of the operands are relations.

One of Codd's 12 rules was that a relational DBMS should have a systematic treatment of NULLS.

That, by itself, seems to me to be an admission that the relational data model is not as abstract as the relational calculus is. Not that I object, mind you. Received on Sat Oct 09 2004 - 13:19:45 CDT