ci高级用法篇之连接多个数据库

在我们的项目中有时可能需要连接不止一个数据库，在ci中如何实现呢？

我们在本地新建了两个数据库，如下截图所示：

修改配置文件database.php文件为如下格式（读者根据自己数据库的情况修改相应参数的配置）：

<?phpdefined('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目录下创建两个文件：score.php

<?phpclass Score extends CI_Model {    private $tableName = 'score';    function __construct()    {        parent::__construct();    }    public function getAllScores(){        return $this->db->get($this->tableName);    }}

和students.php

<?phpclass Students extends CI_Model {    private $tableName = 'students';    function __construct()    {        parent::__construct();    }    public function getAllStudents(){        return $this->db->get($this->tableName);    }}

修改welcome控制器：

<?phpdefined('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('测试结束');}}

访问http://localhost/ci2/地址，浏览器输出如下截图所示：

可以看到ci没有找到score表，我们需要在score.php文件中用

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

显示指明score所在的数据库：

<?phpclass 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);    }}

再次访问访问http://localhost/ci2/地址，输出结果如下截图所示：