Can't delete all the posts from "Guest" accounts?
 

How do I delete all the posts from "Guest" accounts?
I thought that by deleting users it would delete their posts also!

I tried running these queries on my database:
Code:
DELETE FROM post WHERE username = 'Guest'
and
Code:
DELETE FROM thread WHERE postusername = 'Guest'
Ir does not work, only works if I use an actual user name?Help please, I have LOTS of PORN on my forum!!

Thank you!
Joseph