Add new columns as foreign key to existing table in Laravel

For example, we have a table called customers and we want to add a new column called user_id as foreign key to the users table. Here is how to do it.

1. Create a migration file

   php artisan make:migration add_user_id_to_customers_table --table=customers
   

2. Add the following code to the migration file

   public function up()
   {
    Schema::table('customers', function (Blueprint $table) {
        $table->unsignedBigInteger('user_id')->before('created_at');
        $table->foreign('user_id')->references('id')->on('users')->onDelete('SET NULL')
    });
   }
   

   public function down()
   {
    Schema::table('customers', function (Blueprint $table) {
        $table->dropForeign(['user_id']);
        $table->dropColumn('user_id');
    });
   }
   

3. Run the migration

   php artisan migrate