Actually, I wrote a little one the first time I learned PHP way back when. Used a complex ID string to create a comment-style and nested threading structure, with (for then) on-the-fly ability to switch between the two quite easily. I was proud of that, never got anywhere with it because I dropped out of web development for the next 7 years, but eh.

I'm not sure how a forum script should have any longer SQL statement than any other database connected script?
-m