Do you have a need to do a search and replace on an entire column in your MySQL database?
I had to do this recently due to a domain change. Here's the easy way:
UPDATE tablename SET tablefield = replace(tablefield,"findstring","replacestring");
For example, when the shell service I started moved from silenceisdefeat.com to silenceisdefeat.org, I issued the following command to change all of the links in my blog posts:
UPDATE wp_posts SET post_content = replace(post_content,"silenceisdefeat.org","silenceisdefeat.com");
You can do this via the command line, or using a tool like PHPMyAdmin by clicking on the SQL tab. If you're running wp-cache on your WordPress blog, don't forget to clear your cache to see the change take effect.