SQL and Relational Theory, 2nd Edition

PRINCIPLES NOT PRODUCTS

It’s worth taking a few moments to examine the question of why, as I claimed earlier, you as a database professional need to know the relational model. The reason is that the relational model isn’t product specific; instead, it’s concerned with principles. What do I mean by principles? Well, here’s a definition (from Chambers Twentieth Century Dictionary):

principle: a source, root, origin: that which is fundamental: essential nature: theoretical basis: a fundamental truth on which others are founded or from which they spring

The point about principles is: They endure. By contrast, products and technologies (and the SQL language, come to that) change all the time—but principles don’t. For example, suppose you know Oracle; in fact, suppose you’re an expert on Oracle. But if Oracle is all you know, then your knowledge is not necessarily transferable to, say, a DB2 or SQL Server environment (it might even make it harder to make progress in that new environment). But if you know the underlying principles—in other words, if you know the relational model—then you have knowledge and skills that will be transferable: knowledge and skills that you’ll be able to apply in every environment and will never be obsolete.

In this book, therefore, we’ll be concerned with principles, not products, and foundations, not fashion or fads. But I do realize you sometimes have to make compromises and tradeoffs in the real world. For one example, sometimes you might have good pragmatic ...