I occasionally play WOW (World of Warcraft) and as a “Lock” I know that I shouldn’t use hellfire in any instance (bg or not), is a waste of energy and give’s no result.
With MySQL LEFT JOINS is no different. Off course there will be cases where you will be required to use a LEFT JOIN (and in most of these, normalizing the tables would work), but if you can avoid it, the performance gain on the queries is considerable. There are options for not using left joins, but here are a couple:
1. INNER JOINS (should be your first and mostly only option)
2. INNER JOINS …
I’m no MySQL master, but I have received a good article today that give’s a bunch of MySQL optimization tips. Check it out:
http://www.informit.com/articles/article.aspx?p=377652
This article is dedicated to all my friends and co-workers that play with me on WOW and annoy the hell out me when I use a LEFT JOIN 
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