How to Add Foreign Key in Laravel Migration

In this tutorial, you will learn how to add Foreign key in laravel migration with step-by-step example.

To add a foreign key constraint in a Laravel migration, you can utilize the foreign method provided by the Laravel Schema Builder. Here’s an example of how you can add a foreign key constraint using a migration:

Create Parent Table

Create a new migration using the make:migration artisan command:

php artisan make:migration create_organizations_table

Now open the database/migrations/2022_04_01_040458_create_organizations_table.php and put your required column names on it.

 <?php
  
use Illuminate\Database\Migrations\Migration;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Support\Facades\Schema;
  
class CreateOrganizationsTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('organizations', function (Blueprint $table) {
            $table->id();
            $table->string('name');
            $table->timestamps();
        });
    }

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

Create Child Table

Now you need to create another relational table where the parent table id organization_id is added as the foreign key.

php artisan make:migration create_projects_table 

Now open your new generated migration database/migrations/2022_04_01_040458_create_projects_table.php and put the foreign key constraint just like below:

 <?php
  
use Illuminate\Database\Migrations\Migration;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Support\Facades\Schema;
  
class CreateProjectsTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('projects', function (Blueprint $table) {
            $table->id();
            $table->unsignedInteger('organization_id');
            $table->string('name')->nullable();
            $table->timestamps();
  
            $table->foreign('organization_id')
                  ->references('id')
                  ->on('organizations')
                  ->onDelete('cascade');
        });
    }
    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('projects');
    }
}

Run the migration using the migrate artisan command:

php artisan migrate

This will execute the migration and add the foreign key constraint to the specified table.

That’s it! You have now added a foreign key constraint to a table in Laravel using a migration.