Find and Replace with MySql
As exemplified below, MySQL has a very useful function for finding and replacing data.
update [table_name] set [field_name] = replace([field_name], '[search_data]', '[replace_data]');
A real-world example would look something like this:
update page set content = replace(content, 'http://preview.sitehatchery.com', 'http://www.sitehatchery.com');
The nice thing is that the replace function replaces only the part of the string that matches. For instance, if there were multiple instances of "http://preview.sitehatchery.com" in the "content" field of a given record, it would only replace the matching string segments. The surrounding data in the same field would remain unchanged.