如何在codeigniter中使用已连接数据库的数据库连接？

Question

I have already database connected in config folder database.php file. Is there any variable that can simply refers to that MySQLi connection, so that i can use the connection and do manual insertion like-

mysqli_query($alreadyconn, "insert into table ...");

insert() in Codeigniter.com

I know how to insert in codeigniter but i need the above specific case. and here i can not reconnect that database and use the variable.

Any Help Much Appreciated !

Answer 1

Ok. Seems you know about database.php. Will get know some more

$db['default'] = array(
    'dsn'   => '',
    'hostname' => 'localhost', # host
    'username' => '', # Username
    'password' => '', # password
    'database' => '', # Databse name
    'dbdriver' => 'mysqli', # this can be MySQL or MySQLi

Note: Recommend to use MySQLi as db driver.

---

How to connect database??

There are Three ways to archive this

1. Gobally - (path - application/config/autoload.php)

   $autoload['libraries'] = array('database');
   

2. Within the class only.

   class ClassName extends CI_Model 
   {
       public function  __construct()
       {
           parent::__construct();
           $this->load->database();
       } 
   }
   

   Can use in all the methods added within this class

3. Withing Methods only. (Mostly on controllers only)

   class ClassName extends CI_Controller {
   
       public function  __construct()
       {
           parent::__construct();
       }
   
       public function index()
       {
           $this->load->database();
       }
   

   Can use inside the class only

---

What is Query Builder (3.0+) or Active Records(3.0-) ??

This pattern allows information to be retrieved, inserted, and updated in your database with minimal scripting. In some cases only one or two lines of code are necessary to perform a database action. CodeIgniter does not require that each database table be its own class file. It instead provides a more simplified interface.

---

How to query with the database & (Query Builder or Active Records) ??

First Load DB in autoload.php mention above(personally recommended).
Where ever you are in model or controller just use $this->db to get open connection with your DB.
With that you can add Query Builder methods like mention in the codeigniter docs. if you are like to use traditional SQL method, you feel free to use query() (Which is my favorite).

Example

$this->db->query("SELECT * FROM user WHERE name = 'Sparatn' AND ... OR... ");

But this not enough to produce meaningful data. So you have to follow these steps as well

$query = $this->db->query("SELECT * FROM user WHERE name = 'Sparatn' "); # 1
$result  = $query->result_array(); # 2
return $result; #3

In #1 assign the database row data to an variable.
In #2 Convert the #1 to objective array(result_array objective array represent by this).
In #3 return the result to controller.