Summary
UPDATE wp_users SET user_pass = MD5( 'new_password' ) WHERE user_login = 'your-username';Reference
ONEXTRAPIXEL - 2010-01-30 - 13 Useful WordPress SQL Queries You Wish You Knew Earlierhttp://www.onextrapixel.com/2010/01/30/13-useful-wordpress-sql-queries-you-wish-you-knew-earlier/
via
Web活メモ帳 - 2010-02-03 - WordPressで使える知ってると便利な13のSQL文http://blog.verygoodtown.com/2010/02/wordpress-useful-sql-13/