This might be a repost (Hemo is famous for that)

http://books.slashdot.org/article.pl?sid=06/06/07/1458232&mode=nocomment

http://www.oreilly.com/catalog/artofsql/

Sample chapter:
http://www.oreilly.com/catalog/artofsql/chapter/ch04.pdf

Paul

-- If you find yourself using the word "telnet" somewhere, be it in an email or a conversation, please stop and say "I'm sorry, I meant to use ssh instead."