Error establishing a database connection

Hi

I for the first time try to install multisite network for my localhost.
I followed all the steps as mentioned in the codex to create a network but when I was done and it asked me to log in again giving a link itself.. When I clicked it I got the following message “Error establishing a database connection”.. My wordpress is properly installed with database connection I had a site running on it earlier so don’t think it could be a database error. So I am stuck. Please help.

Thanks