From: EN

To: Editor
Date:  June 10, 2003

Here's something I've been thinking about, and I haven't found in your site or writings:

Are the top-down row ordering and left-right column ordering of SQL an example of the Logical/Physical Model confusion surfacing in the design of the DBMS?

The problem with these orderings, in SQL, isn't that they exist, but that the physical ordering is exposed and used by the implementation at the logical level, correct?

 

From: Fabian Pascal

To: EN

 

SQL was designed before it was implemented to rely nonrelationally on bags (instead of tuples), and on left-to-right column ordering. Then it was implemented physically by mapping each logical row to a physical record. The point is that column order was built into SQL before any physical implementation, so whether there is physical order or not, the order is meaningful in SQL (for the practical implications see

A Sweet Disorder in our DATABASE FOUNDATIONS series). That's why the SQL data model is not RM.

There is no meaningful row ordering in SQL.

 

 

Posted 09/19/03

 

 

 

[ABOUT] [QUOTES] [LINKS]