Re: How to find Brothers and Sisters?

From: --CELKO-- <jcelko212_at_earthlink.net>
Date: 7 Jan 2007 20:21:23 -0800
Message-ID: <1168230083.538660.238050@51g2000cwl.googlegroups.com>

>>, I do not recall that Codd's original specification of 1NF allowed NULL. <<

Yep, right from the start in RM1 as rule #3:

3. Systematic treatment of null values

The DBMS is required to support a representation of "missing information and inapplicable information" that is systematic, distinct from all regular values (for example, "distinct from zero or any other number," in the case of numeric values), and independent of data type. It is also implied that such representations must be manipulated by the DBMS in a systematic way. Received on Sun Jan 07 2007 - 22:21:23 CST