change.sql

UPDATE wp_options SET option_value = replace(option_value, 'http://www.old-site.com', 'http://www.new-site.com') WHERE option_name = 'home' OR option_name = 'siteurl';

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

UPDATE wp_posts SET post_content = replace(post_content, ' http://www.ancien-site.com ', ' http://www.nouveau-site.com ');

clean.sql

-- delete spam comments
DELETE from wp_comments WHERE comment_approved = '0';

-- delete 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'

-- delete pingback
DELETE FROM wp_comments WHERE comment_type = 'pingback';

-- identify unused tags
SELECT * From wp_terms wt
INNER JOIN wp_term_taxonomy wtt ON wt.term_id=wtt.term_id WHERE wtt.taxonomy='post_tag' AND wtt.count=0;

-- enable disable pingback
UPDATE wp_posts SET ping_status = 'closed' WHERE post_date < '2012-01-01' AND post_status = 'publish';

-- delete revision
DELETE FROM wp_posts WHERE post_type = "revision";

-- remove short codes
UPDATE wp_post SET post_content = replace(post_content, '[short]', '' ) ;