How to connect database in Codeigniter?

 Connect database in Codeigniter

$active_group = 'default';

$query_builder = TRUE;

$db['default'] = array(

'dsn' => '',

'hostname' => 'localhost', //add server

'username' => 'root', //username

'password' => '',

'database' => 'codelearning', //database name

'dbdriver' => 'mysqli',

'dbprefix' => '',

'pconnect' => FALSE,

'db_debug' => (ENVIRONMENT !== 'production'),

'cache_on' => FALSE,

'cachedir' => '',

'char_set' => 'utf8',

'dbcollat' => 'utf8_general_ci',

'swap_pre' => '',

'encrypt' => FALSE,

'compress' => FALSE,

'stricton' => FALSE,

'failover' => array(),

'save_queries' => TRUE

);