changing the url on the new domain in the database


I have placed all files from the old domain to the new multiste instalation. Do you know where and how i can change the old url with the new url in my database. I will do that with a query but i do not know how to use that so can you tell me which query i need to type and where to accomplish the old url is changed in one time on any location in the new database with the new url.