Changing The Site URL
1) It is possible to set the site URL manually in the wp-config.php file.
define('WP_HOME','http://example.com');
define('WP_SITEURL','http://example.com');
2) If you have access to the site via FTP, then this method will help you quickly get a site back up and running, if you changed those values incorrectly.
Add these two lines to the file, immediately after the initial „<?php” line.
update_option('siteurl','http://example.com');
update_option('home','http://example.com');
From Codex.
