http://www.myguysolutions.com/2010/03/17/11-useful-wordpress-sql-hacks-for-maintaining-your-blog/

http://speckyboy.com/2011/03/23/20-helpful-wordpress-sql-queries-snippets/

http://www.catswhocode.com/blog/10-useful-sql-queries-to-clean-up-your-wordpress-database

http://www.catswhocode.com/blog/wordpress-hacks-and-snippets-to-efficiently-reduce-spam