If you need to change the Magento {{base_url}} manually (hopefully, you have a very good reason to do this) – all you need to do is edit 2 rows in the core_config_data table:

#1 path: web/unsecure/base_url and
#2 path: web/secure/base_url

That’s it! Don’t forget to clear the cache (deleting var/cache should help)