Apache Derby graduates with Sun onboard

TalkBack 5 of 6:

Next »

« Previous

• Thread View
• Flat View

To be relational

All data must be represented as relations and only as relations.

Every tuple in a relation must be unique otherwise it is, by definition, not a relation.

If you do the following:

CREATE TABLE person
(person_id integer NOT NULL primary key,
name varchar(30) NOT NULL);

INSERT INTO person
VALUES (1, "John Smith");

INSERT INTO person
VALUES (2, "John Smith");

SELECT name FROM person;

Gives the result

name
----

John Smith
John Smith

As this result contains duplicates it is not a relation.

Data is thus represented in a way other than relations.

Therefore no DBMS based on SQL can be relational.

If you think this is just nit-picking think about the consequences for interchangeability, that is, from a user or programmer perspective there is no distiction between base relations (tables) and derived relations (views). If you had a view based on the select I have defined above it wouldn't be a relation.

Now think about the implications for allowing views to be updated.

Why has no SQL vendor implemented view updateability beyond the most trivial cases? The answer lies in the complications introduced by SQLs illogical tolerance of duplicates.

Now think about how many thousands of lines of code would be saved if you had an RDBMS with view updateability properly implemented.

Posted by: jorwell   Posted on: 08/04/05 You are currently: a Guest | Members login | Terms of Use

Alert moderator to an offensive message

Subscribe to this discussion via Email or RSS

SponsoredWhite Papers, Webcasts, and Downloads

• Three Steps You Need to Know to Stop Data Loss Varonis Sensitive data exposed to misuse or loss... it is the stuff of nightmares ... Download Now
• The True Costs of Virtual Server Solutions VMware In an economic environment that is repeatedly heralding the message "do ... Download Now
• Reducing Server Total Cost of Ownership with VMware Virtualization Software VMware VMware virtualization enables customers to reduce their server TCO and ... Download Now