Ken,

It's a great article.

Yep as a simple teaching example I get your design. I also get what Joe is saying, although he has often said it better, in that it winds up validating bad design by being used as an example. The "relationship" table (Catalog) is used to connect [Professor] to [Class]. For your next eaxample you might choose something like [SalesOrder] and [SalesOrderActivity].

Joe,

Keep up the good fight! I had one VP take me to task about my penchant for normalization as being "abnormal". I pointed out that we have a mediumn sized database in production that is small, robust, comprehensive, and quick. I learend a lot from your books.

To everybody else,

Take this to heart in that the real answer here is not so much how the joins work but the fact that the way SQL Server processes your execution can surprise you if you are not careful. The key here is that the WHERE clause seems to be processed after all the joins have taken place.