I have found this tool, that will save you time in migrating WordPress databases – check it out

http://interconnectit.com/products/search-and-replace-for-wordpress-databases/

About The Author

Jim Callender is a Freelance Wordpress Developer. Living & working in Brighton. He started working with Wordpress in 2003. Since then has been responsible for delivering high profile sites for a number of large UK design & marketing agencies. His other site is www.jayonline.co.uk