mysqli::real_connect(): (HY000/1049): Unknown data

问题:

I'm new to Codeigniter PHP framework. When I'm testing my application I get 'Unknown database db_name' error. I have browsed through several sites but didn't found solution for the problem as I'm trying the same to connect with wamp's mysql database. Any help would be appreciable.

Following is database.php in config folder: image describing Test database:

$active_group = 'default';
$query_builder = TRUE;

$db['default'] = array(
    'dsn'   => '',
    'hostname' => 'localhost',
    'username' => 'root',
    'password' => '',
    'database' => 'test',
    'dbdriver' => 'mysqli',
    'dbprefix' => '',
    'pconnect' => TRUE,
    'db_debug' => TRUE,
    'cache_on' => FALSE,
    'cachedir' => '',
    'char_set' => 'utf8',
    'dbcollat' => 'utf8_general_ci',
    'swap_pre' => '',
    'encrypt' => FALSE,
    'compress' => FALSE,
    'stricton' => FALSE,
    'failover' => array()
);

回答1:

I was getting same error when i installed new wampserver 3.2.0, it is an evil it installs MariaDB by default and port 3306 is assigned to it , you cannot even change it. I think codeigniter/php tries to connect to this port by default. I used following , it worked for me i.e. hostname => 'localhost:3308'

 $db['default'] = array(
        'dsn'   => '',
        'hostname' => 'localhost:3308',
        'username' => 'root',
        'password' => '',
        'database' => 'soft',
        '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
    );

回答2:

That's what i did to handle whether db exists or not :

First Change this in application/config/database.php

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

to

'db_debug' => FALSE; 

Then add these two in your controller

    $this->load->dbforge();
    $this->load->dbutil();

Then check it in your method

    if( $this->dbutil->database_exists($this->db->database))
    {
        echo 'Database Already Exists';
    }
    else
    {
        if($this->dbforge->create_database($this->db->database))
        {
            echo 'Database created successfully !';
        }else
        {
            print_r($this->db->error());
            /*
               Array ( 
                     [code] => 1007 
                     [message] => Can't create database 'my_db'; database exists 
                    )
           */
        }
    }

回答3:

I was too getting this error. There are 2 fields in application/config/database.php file that should match up with your actual database:

'char_set' => 'utf8',
'dbcollat' => 'utf8_general_ci',

Make sure, the actual DB is of the same type & char_set as mentioned in the above file.