Re: object algebra

> > Codd is correct in that NULLs are an integral part of RDM.
>
> No, he's not right, and Date showed that.

Unless Date was talking about a db with one two-column (one of which one is auto supplied) table, Date is wrong.

> can you actually show me a section or sentence or whatever that
> indicates that NULL is an integral part?

Only the one in Date's books on pg 123 of his 6th Ed. "Codd now regards nulls as an integral part of the relational model"

> Codd invented relational. He stumbled in the implications of his ideas
> later. He was wrong. Date showed that in his book, in the same chapter you
> keep mentioning. What's not clear?

Date's Intro to Dbs, 6th Ed, pg 570, 1st paragrah of Chapter 20 - Missing Info: "the problem of missing information is one that is encountered very frequently in the real world", "are too common in real-world situations and so it is necessary to have some way of dealing with such situations in our formal database system". Chapter Summary: "3VL suffers from the very serious ("showstopper") problem that it does not match reality, that is results that are correct according to 3VL are sometimes incorrect in the real world". Received on Fri Feb 27 2004 - 05:32:25 CET