i am by using this sql.. but it doesn't work

UPDATE wp_options SET option_value = replace(option_value, 'http://old.com, 'http://new.com') WHERE option_name = 'home' OR option_name = 'siteurl';

UPDATE wp_options SET option_value = replace(option_value, 'http://old.com', 'http://new.com') WHERE option_name = 'home' OR option_name = 'siteurl';

UPDATE wp_posts SET guid = replace(guid, 'http://old.com,'http://new.com');

UPDATE wp_posts SET guid = replace(guid, 'http://old.com','http://new.com');

UPDATE wp_posts SET post_content = replace(post_content, 'http://old.com, 'http://new.com');

UPDATE wp_posts SET post_content = replace(post_content, 'http://old.com', 'http://new.com');

UPDATE wp_faquestion SET QuestionAnswer = replace(QuestionAnswer, 'http://old.com, 'http://new.com');

UPDATE wp_faquestion SET QuestionAnswer = replace(QuestionAnswer, 'http://old.com', 'http://new.com');

UPDATE wp_postmeta SET meta_value = replace(meta_value, 'http://old.com, 'http://new.com');

UPDATE wp_postmeta SET meta_value = replace(meta_value, 'http://old.com', 'http://new.com');