Cant connect to databse

As my wordpress is hacked i am trying to make it functional ,now i have lost the way through i came to host it last time,
I have complted uploading the wordpress folder into filezilla also i have imported the databse using cpanel ,i have changed the dbname ,username,password and host ,i have put the host as localhost but there is no luck also i have included these 2 line of codes just after the first line in wp-config.php
define(‘WP_HOME’,’http://sample.com’);
define(‘WP_SITEURL’,’http://sample.com’);

the error is as follows We were able to connect to the database server (which means your username and password is okay) but not able to select the my_database database.