CodeIgniter - Working with Database

Like any other framework, we need to interact with the database very often and CodeIgniter makes this job easy for us. It provides rich set of functionalities to interact with database.
In this section, we will understand how the CRUD (Create, Read, Update, Delete) functions work with CodeIgniter. We will use stud table to select, update, delete, and insert the data in stud table.
We can connect to database in the following two way −
Automatic Connecting − Automatic connection can be done by using the file application/config/autoload.php. Automatic connection will load the database for each and every page. We just need to add the database library as shown below −
Automatic Connecting − Automatic connection can be done by using the file application/config/autoload.php. Automatic connection will load the database for each and every page. We just need to add the database library as shown below −
$autoload['libraries'] = array(‘database’);

Manual Connecting − If you want database connectivity for only some of the pages, then we can go for manual connecting. We can connect to database manually by adding the following line in any class.
Manual Connecting − If you want database connectivity for only some of the pages, then we can go for manual connecting. We can connect to database manually by adding the following line in any class.
$this->load->database();

Here, we are not passing any argument because everything is set in the database config file application/config/database.php
To insert a record in the database, the insert() function is used as shown in the following table −
Syntax
Parameters
$table (string) − Table name
$table (string) − Table name
$set (array) − An associative array of field/value pairs
$set (array) − An associative array of field/value pairs
$escape (bool) − Whether to escape values and identifiers
$escape (bool) − Whether to escape values and identifiers
Returns
Return Type
The following example shows how to insert a record in stud table. The $data is an array in which we have set the data and to insert this data to the table stud, we just need to pass this array to the insert function in the 2nd argument.
$data = array( 
   'roll_no' => ‘1’, 
   'name' => ‘Virat’ 
); 

$this->db->insert("stud", $data);
To update a record in the database, the update() function is used along with set() and where() functions as shown in the tables below. The set() function will set the data to be updated.
Syntax
Parameters
$key (mixed) − Field name, or an array of field/value pairs
$key (mixed) − Field name, or an array of field/value pairs
$value (string) − Field value, if $key is a single field
$value (string) − Field value, if $key is a single field
$escape (bool) − Whether to escape values and identifiers
$escape (bool) − Whether to escape values and identifiers
Returns
Return Type
The where() function will decide which record to update.
Syntax
Parameters
$key (mixed) − Name of field to compare, or associative array
$key (mixed) − Name of field to compare, or associative array
$value (mixed) − If a single key, compared to this value
$value (mixed) − If a single key, compared to this value
$escape (bool) − Whether to escape values and identifiers
$escape (bool) − Whether to escape values and identifiers
Returns
Return Type
Finally, the update() function will update data in the database.
Syntax
Parameters
$table (string) − Table name
$table (string) − Table name
$set (array) − An associative array of field/value pairs
$set (array) − An associative array of field/value pairs
$where (string) − The WHERE clause
$where (string) − The WHERE clause
$limit (int) − The LIMIT clause
$limit (int) − The LIMIT clause
Returns
Return Type
$data = array( 
   'roll_no' => ‘1’, 
   'name' => ‘Virat’ 
); 

$this->db->set($data); 
$this->db->where("roll_no", ‘1’); 
$this->db->update("stud", $data);
To delete a record in the database, the delete() function is used as shown in the following table −
Syntax
Parameters
$table (mixed) − The table(s) to delete from; string or array
$table (mixed) − The table(s) to delete from; string or array
$where (string) − The WHERE clause
$where (string) − The WHERE clause
$limit (int) − The LIMIT clause
$limit (int) − The LIMIT clause
$reset_data (bool) − TRUE to reset the query “write” clause
$reset_data (bool) − TRUE to reset the query “write” clause
Returns
Return Type
Use the following code to to delete a record in the stud table. The first argument  indicates the name of the table to delete record and the second argument decides which record to delete.
$this->db->delete("stud", "roll_no = 1");

To select a record in the database, the get function is used, as shown in the following table −
Syntax
Parameters
$table (string) − The table to query array
$table (string) − The table to query array
$limit (int) − The LIMIT clause
$limit (int) − The LIMIT clause
$offset (int) − The OFFSET clause
$offset (int) − The OFFSET clause
Returns
Return Type
Use the following code to get all the records from the database. The first statement fetches all the records from “stud” table and returns the object, which will be stored in $query object. The second statement calls the result() function with $query object to get all the records as array.
$query = $this->db->get("stud"); 
$data['records'] = $query->result();
Database connection can be closed manually, by executing the following code −
$this->db->close(); 

Create a controller class called Stud_controller.php and save it at application/controller/Stud_controller.php
Here is a complete example, wherein all of the above-mentioned operations are performed. Before executing the following example, create a database and table as instructed at the starting of this chapter and make necessary changes in the database config file stored at application/config/database.php
<?php 
   class Stud_controller extends CI_Controller {
	
      function __construct() { 
         parent::__construct(); 
         $this->load->helper('url'); 
         $this->load->database(); 
      } 
  
      public function index() { 
         $query = $this->db->get("stud"); 
         $data['records'] = $query->result(); 
			
         $this->load->helper('url'); 
         $this->load->view('Stud_view',$data); 
      } 
  
      public function add_student_view() { 
         $this->load->helper('form'); 
         $this->load->view('Stud_add'); 
      } 
  
      public function add_student() { 
         $this->load->model('Stud_Model');
			
         $data = array( 
            'roll_no' => $this->input->post('roll_no'), 
            'name' => $this->input->post('name') 
         ); 
			
         $this->Stud_Model->insert($data); 
   
         $query = $this->db->get("stud"); 
         $data['records'] = $query->result(); 
         $this->load->view('Stud_view',$data); 
      } 
  
      public function update_student_view() { 
         $this->load->helper('form'); 
         $roll_no = $this->uri->segment('3'); 
         $query = $this->db->get_where("stud",array("roll_no"=>$roll_no));
         $data['records'] = $query->result(); 
         $data['old_roll_no'] = $roll_no; 
         $this->load->view('Stud_edit',$data); 
      } 
  
      public function update_student(){ 
         $this->load->model('Stud_Model');
			
         $data = array( 
            'roll_no' => $this->input->post('roll_no'), 
            'name' => $this->input->post('name') 
         ); 
			
         $old_roll_no = $this->input->post('old_roll_no'); 
         $this->Stud_Model->update($data,$old_roll_no); 
			
         $query = $this->db->get("stud"); 
         $data['records'] = $query->result(); 
         $this->load->view('Stud_view',$data); 
      } 
  
      public function delete_student() { 
         $this->load->model('Stud_Model'); 
         $roll_no = $this->uri->segment('3'); 
         $this->Stud_Model->delete($roll_no); 
   
         $query = $this->db->get("stud"); 
         $data['records'] = $query->result(); 
         $this->load->view('Stud_view',$data); 
      } 
   } 
?>
Create a model class called Stud_Model.php and save it in application/models/Stud_Model.php
<?php 
   class Stud_Model extends CI_Model {
	
      function __construct() { 
         parent::__construct(); 
      } 
   
      public function insert($data) { 
         if ($this->db->insert("stud", $data)) { 
            return true; 
         } 
      } 
   
      public function delete($roll_no) { 
         if ($this->db->delete("stud", "roll_no = ".$roll_no)) { 
            return true; 
         } 
      } 
   
      public function update($data,$old_roll_no) { 
         $this->db->set($data); 
         $this->db->where("roll_no", $old_roll_no); 
         $this->db->update("stud", $data); 
      } 
   } 
?> 
Create a view file called Stud_add.php and save it in application/views/Stud_add.php
<!DOCTYPE html> 
<html lang = "en">
 
   <head> 
      <meta charset = "utf-8"> 
      <title>Students Example</title> 
   </head> 
   <body> 
         <?php 
            echo form_open('Stud_controller/add_student');
            echo form_label('Roll No.'); 
            echo form_input(array('id'=>'roll_no','name'=>'roll_no')); 
            echo "<br/>"; 
			
            echo form_label('Name'); 
            echo form_input(array('id'=>'name','name'=>'name')); 
            echo "<br/>"; 
			
            echo form_submit(array('id'=>'submit','value'=>'Add')); 
            echo form_close(); 
         ?> 
   </body>
</html>
Create a view file called Stud_edit.php and save it in application/views/Stud_edit.php
<!DOCTYPE html> 
<html lang = "en">
 
   <head> 
      <meta charset = "utf-8"> 
      <title>Students Example</title> 
   </head> 
	
   <body> 
      <form method = "" action = "">
		
         <?php 
            echo form_open('Stud_controller/update_student'); 
            echo form_hidden('old_roll_no',$old_roll_no); 
            echo form_label('Roll No.'); 
            echo form_input(array('id'⇒'roll_no',
               'name'⇒'roll_no','value'⇒$records[0]→roll_no)); 
            echo "
            "; 

            echo form_label('Name'); 
            echo form_input(array('id'⇒'name','name'⇒'name',
               'value'⇒$records[0]→name)); 
            echo "
            "; 

            echo form_submit(array('id'⇒'sub mit','value'⇒'Edit')); 
            echo form_close();
         ?> 
			
      </form> 
   </body>
	
</html>
Create a view file called Stud_view.php and save it in application/views/Stud_view.php
<!DOCTYPE html> 
<html lang = "en">
 
   <head> 
      <meta charset = "utf-8"> 
      <title>Students Example</title> 
   </head>
	
   <body> 
      <a href = "<?php echo base_url(); ?>
         index.php/stud/add_view">Add</a>
		
      <table border = "1"> 
         <?php 
            $i = 1; 
            echo "<tr>"; 
            echo "<td>Sr#</td>"; 
            echo "<td>Roll No.</td>"; 
            echo "<td>Name</td>"; 
            echo "<td>Edit</td>"; 
            echo "<td>Delete</td>"; 
            echo "<tr>"; 
				
            foreach($records as $r) { 
               echo "<tr>"; 
               echo "<td>".$i++."</td>"; 
               echo "<td>".$r->roll_no."</td>"; 
               echo "<td>".$r->name."</td>"; 
               echo "<td><a href = '".base_url()."index.php/stud/edit/"
                  .$r->roll_no."'>Edit</a></td>"; 
               echo "<td><a href = '".base_url()."index.php/stud/delete/"
                  .$r->roll_no."'>Delete</a></td>"; 
               echo "<tr>"; 
            } 
         ?>
      </table> 
		
   </body>
	
</html>
Make the following change in the route file at application/config/routes.php and add the following line at the end of file.
$route['stud'] = "Stud_controller"; 
$route['stud/add'] = 'Stud_controller/add_student'; 
$route['stud/add_view'] = 'Stud_controller/add_student_view'; 
$route['stud/edit/(\d+)'] = 'Stud_controller/update_student_view/$1'; 
$route['stud/delete/(\d+)'] = 'Stud_controller/delete_student/$1';

Now, let us execute this example by visiting the following URL in the browser. Replace the yoursite.com with your URL.
http://yoursite.com/index.php/stud

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