I think you are confusing the persona in which the article is written with the actual person who wrote it.
Thanks. I appreciate the support. However, the article is substantively correct. I wasn't at all confused about what a join is, but I was indeed surprised by the result of moving what I took to be a non-join condition from the WHERE clause into the FROM clause of a query that was doing an outer-join.
To address the first poster, I don't see why anyone should find it "scary" that I managed to learn something new that I didn't know before. Just because I edit and write database books doesn't make me omniscient. And it would be utterly foolish for me to stop learning just because I'm an editor. For that matter, I'm actually learning a lot this week: I'm in San Francisco attending a Hotsos Clinic (about Oracle tuning) put on by Cary Millsap.
The scary part, for me at least, was to write the article in a way that conveyed my initial ignorance, and then my subseqent enlightenment. I could have written the article such that I appeared to know all along what I was talking about. Instead, I shared my learning experience just as it really happened.