ci高级使用方法篇之连接多个数据库

在我们的项目中有时可能须要连接不止一个数据库。在ci中怎样实现呢？

我们在本地新建了两个数据库，例如以下截图所看到的：

改动配置文件database.php文件为例如以下格式（读者依据自己数据库的情况改动对应參数的配置）：

<?php
defined('BASEPATH') OR exit('No direct script access allowed');

/*
| -------------------------------------------------------------------
| DATABASE CONNECTIVITY SETTINGS
| -------------------------------------------------------------------
| This file will contain the settings needed to access your database.
|
| For complete instructions please consult the 'Database Connection'
| page of the User Guide.
|
| -------------------------------------------------------------------
| EXPLANATION OF VARIABLES
| -------------------------------------------------------------------
|
|	['dsn']      The full DSN string describe a connection to the database.
|	['hostname'] The hostname of your database server.
|	['username'] The username used to connect to the database
|	['password'] The password used to connect to the database
|	['database'] The name of the database you want to connect to
|	['dbdriver'] The database driver. e.g.: mysqli.
|			Currently supported:
|				 cubrid, ibase, mssql, mysql, mysqli, oci8,
|				 odbc, pdo, postgre, sqlite, sqlite3, sqlsrv
|	['dbprefix'] You can add an optional prefix, which will be added
|				 to the table name when using the  Query Builder class
|	['pconnect'] TRUE/FALSE - Whether to use a persistent connection
|	['db_debug'] TRUE/FALSE - Whether database errors should be displayed.
|	['cache_on'] TRUE/FALSE - Enables/disables query caching
|	['cachedir'] The path to the folder where cache files should be stored
|	['char_set'] The character set used in communicating with the database
|	['dbcollat'] The character collation used in communicating with the database
|				 NOTE: For MySQL and MySQLi databases, this setting is only used
| 				 as a backup if your server is running PHP < 5.2.3 or MySQL < 5.0.7
|				 (and in table creation queries made with DB Forge).
| 				 There is an incompatibility in PHP with mysql_real_escape_string() which
| 				 can make your site vulnerable to SQL injection if you are using a
| 				 multi-byte character set and are running versions lower than these.
| 				 Sites using Latin-1 or UTF-8 database character set and collation are unaffected.
|	['swap_pre'] A default table prefix that should be swapped with the dbprefix
|	['encrypt']  Whether or not to use an encrypted connection.
|	['compress'] Whether or not to use client compression (MySQL only)
|	['stricton'] TRUE/FALSE - forces 'Strict Mode' connections
|							- good for ensuring strict SQL while developing
|	['failover'] array - A array with 0 or more data for connections if the main should fail.
|	['save_queries'] TRUE/FALSE - Whether to "save" all executed queries.
| 				NOTE: Disabling this will also effectively disable both
| 				$this->db->last_query() and profiling of DB queries.
| 				When you run a query, with this setting set to TRUE (default),
| 				CodeIgniter will store the SQL statement for debugging purposes.
| 				However, this may cause high memory usage, especially if you run
| 				a lot of SQL queries ... disable this to avoid that problem.
|
| The $active_group variable lets you choose which connection group to
| make active.  By default there is only one group (the 'default' group).
|
| The $query_builder variables lets you determine whether or not to load
| the query builder class.
*/

$active_group = 'test';//默认连接test数据库
$active_record = TRUE;//是否开启active record

$db['test'] = array(
	'dsn'	=> '',
	'hostname' => 'localhost',
	'username' => 'root',
	'password' => '',
	'database' => 'test',
	'dbdriver' => 'mysqli',
	'dbprefix' => '',
	'pconnect' => FALSE,
	'db_debug' => TRUE,
	'cache_on' => FALSE,
	'cachedir' => '',
	'char_set' => 'utf8',
	'dbcollat' => 'utf8_general_ci',
	'swap_pre' => '',
	'encrypt' => FALSE,
	'compress' => FALSE,
	'stricton' => FALSE,
	'failover' => array(),
	'save_queries' => TRUE
);
//test2数据库相关配置
$db['test2'] = array(
	'dsn'	=> '',
	'hostname' => 'localhost',
	'username' => 'root',
	'password' => '',
	'database' => 'test2',
	'dbdriver' => 'mysqli',
	'dbprefix' => '',
	'pconnect' => FALSE,
	'db_debug' => TRUE,
	'cache_on' => FALSE,
	'cachedir' => '',
	'char_set' => 'utf8',
	'dbcollat' => 'utf8_general_ci',
	'swap_pre' => '',
	'encrypt' => FALSE,
	'compress' => FALSE,
	'stricton' => FALSE,
	'failover' => array(),
	'save_queries' => TRUE
);

在applicaton/model文件夹下创建两个文件：score.php

<?php
class Score extends CI_Model {

    private $tableName = 'score';

    function __construct()
    {
        parent::__construct();
    }

    public function getAllScores(){
        return $this->db->get($this->tableName);
    }
}

和students.php

<?php
class Students extends CI_Model {

    private $tableName = 'students';

    function __construct()
    {
        parent::__construct();
    }

    public function getAllStudents(){
        return $this->db->get($this->tableName);
    }
}

改动welcome控制器：

<?

php
defined('BASEPATH') OR exit('No direct script access allowed');

class Welcome extends ci_Controller {

	/**
	 * Index Page for this controller.
	 *
	 * Maps to the following URL
	 * 		http://example.com/index.php/welcome
	 *	- or -
	 * 		http://example.com/index.php/welcome/index
	 *	- or -
	 * Since this controller is set as the default controller in
	 * config/routes.php, it's displayed at http://example.com/
	 *
	 * So any other public methods not prefixed with an underscore will
	 * map to /index.php/welcome/<method_name>
	 * @see http://codeigniter.com/user_guide/general/urls.html
	 */
	public function __construct(){
		parent::__construct();
		$this->load->model('students');
		$this->load->model('score');
	}

	public function index()
	{
		var_dump($this->students->getAllStudents()->result());
		var_dump($this->score->getAllScores()->result());
		die('測试结束');
	}
}

訪问http://localhost/ci2/地址。浏览器输出例如以下截图所看到的：

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能够看到ci没有找到score表，我们须要在score.php文件里用

$this->db = $this->load->database('test2', TRUE);

显示指明score所在的数据库：

<?php
class Score extends CI_Model {

    private $tableName = 'score';
    private $db;

    function __construct()
    {
        parent::__construct();
        $this->db = $this->load->database('test2', TRUE);
    }

    public function getAllScores(){
        return $this->db->get($this->tableName);
    }
}

再次訪问訪问http://localhost/ci2/地址。输出结果例如以下截图所看到的：