Re: OID's vs Relational Keys?
From: -CELKO- <jcelko212_at_earthlink.net>
Date: 22 Dec 2005 10:37:04 -0800
Message-ID: <1135276624.698019.131500_at_g47g2000cwa.googlegroups.com>
Date: 22 Dec 2005 10:37:04 -0800
Message-ID: <1135276624.698019.131500_at_g47g2000cwa.googlegroups.com>
I have invented the term "physical locator" to cover things like the classic hardware pointers you are talking about, row_id within a table structure, hash table values, etc. Anything that:
- Is not an attribute in the reality of the data model. in the Relational keys are a set of attributes by definition. Nothing to do with physical storage.
- They are generated inside the machine and depend on the internal state of the machine at creation time. Nothing to do with the data model or the real world.
And I do believe in duplicate values, but not duplicate data elements. So did Dr. Codd when he introduced a "Degree of Duplication" operation in his second version of RM. Codd also defined a surrogate as being hidden from users, so things like auto-numbering and IDENTITY do not qualify in most products. Received on Thu Dec 22 2005 - 19:37:04 CET