How to Create Relations in Laravel Migration?

Laravel relation provides almost all feature to create the database schema and one of best feature is create relations in laravel migration. As We know relations are used to create the associations between the tables and there is three types of relations in mysql which is one-to-one, one-to-many, and many-to-many. Relations consist foreign key and primary key.

In our this article i will show you to create relations between the tables in laravel migration. To create the relations we need to create the primary key and foreign key. Primary key is used to create the relation with foreign key.

In this post we will take a simple example in which we will create two tables and primary key and foreign key for relation. This example will work all version of laravel 5, laravel 6, laravel 7, laravel 8 and laravel 9.

Let’s have simple syntax of create relation using foreign, references and on methods of laravel Schema class.

Here is the syntax

$table->foreign('user_id')->references('id')->on('users');

Here, we used foreign method which accepts name of column in child table, references to define the name of column in parent table or reference table and on to define the name of table.

We will use the php artisan command to generate the Laravel migration and php artisan migrate command to modify the table.

Let’s understand it step by step

Step 1 : Generate migration file

To generate the migration file we will use the laravel artisan command so open the terminal in project and run below command

php artisan make:migration movies_table

and another table users

php artisan make:migration create_users_table

Above command will create a migration file in folder database/migrations

Output: 
Created Migration: 2022_06_30_174050_movies_table
Created Migration: 2022_06_30_174050_create_users_table

Step 2 : Open generated migration file and update

In the last step we created a migration file using the artisan command and now we wanted to Create Relations between the tables so adding a user_id column as integer.

so let’s open the file and start editing

<?php

use Illuminate\Database\Migrations\Migration;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Support\Facades\Schema;

class CreateUsersTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('users', function (Blueprint $table) {
            $table->id();
            $table->string('email')->unique();
            $table->timestamps();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
         Schema::dropIfExists('users');
    }
}

and another movies table

<?php

use Illuminate\Database\Migrations\Migration;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Support\Facades\Schema;

class CreateMoviesTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('movies', function (Blueprint $table) {
            $table->id();
            $table->string('email')->unique();
            $table->integer('user_id');
            $table->string('title');
            $table->foreign('user_id')->references('id')->on('users');
            $table->timestamps();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
         Schema::dropIfExists('movies');
    }
}

as you can see we have created string field using $table->foreign('user_id')->references('id')->on('users'); syntax and created simple users table so we can connect association between users and movies. here users is parent or reference table, movies is child or foreign table and so id is column of parent users table and user_id is child table column.

Step 3 : Run Migration

In this step we will execute our migration in database using below command

php artisan migrate

This will create table in database and the output

Output: 
Migrating: 2022_02_15_174050_movies_table
Migrated:  2022_02_15_174050_movies_table (20.08ms)
Migrating: 2022_02_15_174050_create_users_table
Migrated:  2022_02_15_174050_create_users_table (20.08ms)

Also Read : How to delete column in laravel migration ?