Wordpress SQL - Delete Revisions

# SOURCE: http://lesterchan.net/wordpress/2008/07/17/how-to-turn-off-post-revision-in-wordpress-26/
DELETE a,b,c FROM wp_posts a
LEFT JOIN wp_term_relationships b ON (a.ID = b.object_id)
LEFT JOIN wp_postmeta c ON (a.ID = c.post_id)
WHERE a.post_type = 'revision'