Database tricks

Updating links in old posts when things change
Moving WordPress

UPDATE wp_posts SET post_content = replace(post_content, 'http://www.old-domain.com', 'http://www.new-domain.com');

UPDATE wp_posts SET guid = replace(guid, 'http://www.old-domain.com', 'http://www.new-domain.com');

How To Turn Off Post Revision

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'