533968 help migrating Wordpress to new domain 2

Hi i have transferred all wordpress files from my development domain to my live domain but its coming up with a Error establishing database connection error I have checked wp-config to make sure i have the correct database settings etc and have checked the database phpadmin to check that the database has been installed but cant find anything that would cause this error I need help geting this site installed. Its a quick project for someone who knows what they are doing. also i am using wordpress multisite and have installed the domain mapping plugin I will also need a little assistance in getting my zoned subdomains to show up in the right areas of the site ie [login to view URL] will become [login to view URL] and [login to view URL] will become [login to view URL] etc etc. I basically just need help getting this site installed correctly to work with the new domains etc.