连接到数据库并执行查询

我本来想在他们的论坛上发布这个,但他们现在好像不在了。

$mydb  = Database::instance('mydb');
$query = DB::select()->from('codes')->where('name', '=', 'PHP'); 

1) 在使用我在中定义的自定义数据库实例时,我看不出这一点数据库.php. 它总是使用默认值。我怎么知道?

mysql_connect(): Access denied for user ''@'localhost' (using password: NO) ~ MODPATH\database\classes\kohana\database\mysql.php [ 56 ]

2) 我有点困惑,因为根据他们的教程,execute($mydb)应该不是必需的。。。但我看到一些帖子暗示这是真的。是哪一个?

配置文件:

<?php defined('SYSPATH') or die('No direct access allowed.');

return array
(
    'default' => array
    (
        'type'       => 'mysql',
        'connection' => array(
            /**
             * The following options are available for MySQL:
             *
             * string   hostname     server hostname, or socket
             * string   database     database name
             * string   username     database username
             * string   password     database password
             * boolean  persistent   use persistent connections?
             *
             * Ports and sockets may be appended to the hostname.
             */
            'hostname'   => 'localhost',
            'database'   => 'kohana',
            'username'   => FALSE,
            'password'   => FALSE,
            'persistent' => FALSE,
        ),
        'table_prefix' => '',
        'charset'      => 'utf8',
        'caching'      => FALSE,
        'profiling'    => TRUE,
    ),
    'alternate' => array(
        'type'       => 'pdo',
        'connection' => array(
            /**
             * The following options are available for PDO:
             *
             * string   dsn         Data Source Name
             * string   username    database username
             * string   password    database password
             * boolean  persistent  use persistent connections?
             */
            'dsn'        => 'mysql:host=localhost;dbname=kohana',
            'username'   => 'root',
            'password'   => 'r00tdb',
            'persistent' => FALSE,
        ),
        /**
         * The following extra options are available for PDO:
         *
         * string   identifier  set the escaping identifier
         */
        'table_prefix' => '',
        'charset'      => 'utf8',
        'caching'      => FALSE,
        'profiling'    => TRUE,
    ),
    'mydb' => array(
        'type'       => 'mysql',
        'connection' => array(
            'hostname'   => '127.0.0.1',
            'username'   => 'test',
            'password'   => 'test',
            'persistent' => FALSE,
            'database'   => 'mydb',
        ),
        'table_prefix' => '',
        'charset'      => 'utf8',
        'profiling'    => TRUE,
    ),