Working with MySQL Inner Join in CodeIgniter 4

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When we work with MySQL Queries, then definitely for some relational data we need to work with Joins. Inside this article we will see the concept of Inner Join in CodeIgniter 4.

Joins in CodeIgniter 4 is the connection between one and more tables to get data. In MySQL we have Inner join, Left join, Right join, Outer join.

We will see the concept of Inner Join in this CodeIgniter 4 article.

Learn More –

Let’s get started.

Types of Joins available in CodeIgniter 4

In CodeIgniter 4 application, as per the documentation we have 3 types of joins available. Here are the followings –

  • Inner Join
  • Left Join
  • Right Join

What is Inner Join?

Inner Join – This join brings the data on the basis of a common value condition between two or more than two tables. According to matched condition it will bring all data what we expected for. It remove those rows from result set which has no matched condition.

How can we use inside an application and get relational data we will see by making an application. Let’s create an application in which we use Inner Join.

CodeIgniter 4 Installation

To create a CodeIgniter 4 setup run this given command into your shell or terminal. Please make sure composer should be installed.

composer create-project codeigniter4/appstarter codeigniter-4

Assuming you have successfully installed application into your local system.

Environment (.env) Setup

When we install CodeIgniter 4, we will have env file at root. To use the environment variables means using variables at global scope we need to do env to .env

Either we can do via renaming file as simple as that. Also we can do by terminal command.

Open project in terminal

cp env .env

Above command will create a copy of env file to .env file. Now we are ready to use environment variables.

Enable Development Mode

CodeIgniter starts up in production mode by default. You need to make it in development mode to see any error if you are working with application.

Open .env file from root.

# CI_ENVIRONMENT = production

 // Do it to 
CI_ENVIRONMENT = development

Now application is in development mode.

Create Database

To create a database, either we can create via Manual tool of PhpMyadmin or by means of a mysql command.

We will use MySQL command to create database. Run this command into Sql tab of PhpMyAdmin.

CREATE DATABASE codeigniter4_app;

Successfully, we have created a database.

Create Database Table

Next, we need tables. That table will be responsible to store data.

Let’s create two tables with some columns.

CREATE TABLE `tbl_users` (
 `name` varchar(120) DEFAULT NULL,
 `email` varchar(120) DEFAULT NULL,
 `phone_no` varchar(120) DEFAULT NULL,

CREATE TABLE `tbl_courses` (
 `name` varchar(120) NOT NULL,
 `user_id` int(11) NOT NULL,

Table tbl_courses contains user_id column on the basis of which we are going to make use of join. Successfully, we have created two tables.

Let’s insert some dummy data into these tables.

Database Connection

Open .env file from project root.

Search for DATABASE. You should see the connection environment variables into it. Put your updated details of database connection string values.


database.default.hostname = localhost
database.default.database = codeigniter4_app
database.default.username = admin
database.default.password = admin
database.default.DBDriver = MySQLi
database.default.DBPrefix =
database.default.port = 3306

Now, database successfully connected with the application.

Creating Test data for Application

Here we have some sql queries, you need to copy and run into database. It will inserts data into tables.

Test data for tbl_users

-- Dumping data for table `tbl_users`
INSERT INTO `tbl_users` (`id`, `name`, `email`, `phone_no`, `created_at`) VALUES
(1, 'Sanjay', '', '8527419630', '2020-09-10 13:19:38'),
(2, 'Vijay', '', '9875643125', '2020-09-25 11:33:00'),
(3, 'Ashish Kumar', '', '7896541230', '2020-09-25 11:33:17');

Test data for tbl_courses

-- Dumping data for table `tbl_courses`

INSERT INTO `tbl_courses` (`id`, `name`, `user_id`) VALUES
(1, 'Learn CodeIgniter 4', 1),
(2, 'Learn PHP', 2),
(3, 'Learn CakePHP 4', 30),
(4, 'Learn Laravel', 35);

To Learn about Seeders in CodeIgniter 4, Click here.

Create Routes

Open Routes.php from /app/Config. Add this route into this file.


$routes->get('inner-join', 'Site::innerJoinMethod');

Create Controller


Open project into terminal and run this spark command to create controller.

$ php spark make:controller Site

It will create Site.php at /app/Controllers folder.

Open Site.php and write this complete code into it.


namespace App\Controllers;

use App\Controllers\BaseController;

class Site extends BaseController
    private $db;

    public function __construct()
        $this->db = db_connect(); // Loading database
        // OR $this->db = \Config\Database::connect();

    public function innerJoinMethod()
        $builder = $this->db->table("tbl_users as user");
        $builder->select('user.*, as course_name');
        $builder->join('tbl_courses as course', ' = course.user_id');
        $data = $builder->get()->getResult();

        echo "<pre>";
        // To print query
        // $this->db->getLastQuery();


Behind the scene executed query is –

SELECT `user`.*, `course`.`name` as `course_name` FROM `tbl_users` as `user` JOIN `tbl_courses` as `course` ON `user`.`id` = `course`.`user_id`

Application Testing

Open project terminal and start development server via command:

php spark serve

URL – http://localhost:8080/inner-join

Have a look output –

We are getting only matched rows according to the condition = course.user_id

We hope this article helped you to learn MySQL Inner join in codeigniter 4 in a very detailed way.

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Sanjay KumarHello friends, I am Sanjay Kumar a Web Developer by profession. Additionally I'm also a Blogger, Youtuber by Passion. I founded Online Web Tutor and Skillshike platforms. By using these platforms I am sharing the valuable knowledge of Programming, Tips and Tricks, Programming Standards and more what I have with you all. Read more