Re: Poll: What percentage advantage are RDBMS vendors taking of the RM?

mountain man wrote:
> What I am trying to ask is "How *relational* are DB2, Oracle and SQL Server
> according to the principles of the relational model?
>
> People assert that these SQL-DBMS are "the best we have at the moment"
> and that they are not ("Fully") relational. I want to understand just HOW
> MUCH they are not fully relational, as a ball-park rough-as-guts estimate.
>
> Is it 10% or is it 90%. ?

Well here's a list of Codd's 12 rules, which are general guidelines for a DBMS to be thought of as relational:

http://www.wildewood.co.uk/comp/more/codds_rules.html

I'd say most SQL-DBMSs are inspired by this, although some of the rules clearly aren't followed. But we're getting there slowly.

It's easy to criticise DBMS designers for not building a fully-relational product, but I think the practical problems are bigger than we might think. It's a serious level of abstraction, especially when you consider that many DBMSs were started years ago when computer were many orders of magnitude less powerful than they are today.

I'll give them 8 out of 10 for effort. :)

Paul. Received on Tue Jun 07 2005 - 17:43:32 CEST