Migration Problem: Cannot add foreign key constraint in laravel

Question

I'm trying to create foreign keys in Laravel 5.7 however when I migrate my table using artisan i am thrown the following error:

Illuminate\Database\QueryException:

SQLSTATE[HY000]: General error: 1215 Cannot add foreign key constraint (SQL: alter table gateway_transactions add constraint gateway_transactions_user_id_foreign foreign key (user_id) references users (id) on delete CASCADE)

my migration :

    public function up()
    {
        Schema::create('gateway_transactions', function (Blueprint $table) {
            $table->engine = "innoDB";
            $table->unsignedBigInteger('id', true);
            $table->integer('user_id')->unsigned();
            $table->enum('provider', \Parsisolution\Gateway\GatewayManager::availableDrivers());
            $table->decimal('amount', 15, 2);
            $table->integer('order_id')->nullable();
            $table->string('currency', 3)->nullable();
            $table->string('ref_id', 100)->nullable();
            $table->string('tracking_code', 50)->nullable();
            $table->string('card_number', 50)->nullable();
            $table->enum('status', \Parsisolution\Gateway\Transaction::availableStates())
                ->default(\Parsisolution\Gateway\Transaction::STATE_INIT);
            $table->string('ip', 20)->nullable();
            $table->json('extra')->nullable();
            $table->timestamp('paid_at')->nullable();
            $table->nullableTimestamps();
            $table->softDeletes();
        });
        Schema::table('gateway_transactions', function(Blueprint $table) {
            $table->foreign('user_id')->references('id')->on('users')->onDelete('CASCADE');
        });
    }

users migration :

        Schema::create(config('access.table_names.users'), function (Blueprint $table) {
            $table->increments('id');
            $table->uuid('uuid');
            $table->string('first_name')->nullable();
            $table->string('last_name')->nullable();
            $table->string('email')->unique();
            $table->string('avatar_type')->default('gravatar');
            $table->string('avatar_location')->nullable();
            $table->string('password')->nullable();
            $table->timestamp('password_changed_at')->nullable();
            $table->tinyInteger('active')->default(1)->unsigned();
            $table->string('confirmation_code')->nullable();
            $table->boolean('confirmed')->default(config('access.users.confirm_email') ? false : true);
            $table->string('timezone')->nullable();
            $table->text('National_Code')->nullable();
            $table->char('phone_number', 11)->nullable()->unique();  
            $table->integer('phone_verify')->default(0);
            $table->char('mobile_number', 11)->nullable()->unique();  
            $table->integer('mobile_verify')->default(0);
            $table->text('state')->nullable();
            $table->text('city')->nullable();
            $table->text('address')->nullable();
            $table->text('path')->nullable();
            $table->char('postal_code', 10)->nullable();
            $table->timestamp('last_login_at')->nullable();
            $table->string('last_login_ip')->nullable();
            $table->rememberToken();
            $table->timestamps();
            $table->softDeletes();
        });

Answer 1

Change your code for this :

public function up()
{
    Schema::create('gateway_transactions', function (Blueprint $table) {
        $table->engine = "innoDB";
        $table->unsignedBigInteger('id', true);
        $table->integer('user_id')->unsigned();
        $table->foreign('user_id')->references('id')->on('users')->onDelete('CASCADE');
        $table->enum('provider', \Parsisolution\Gateway\GatewayManager::availableDrivers());
        $table->decimal('amount', 15, 2);
        $table->integer('order_id')->nullable();
        $table->string('currency', 3)->nullable();
        $table->string('ref_id', 100)->nullable();
        $table->string('tracking_code', 50)->nullable();
        $table->string('card_number', 50)->nullable();
        $table->enum('status', \Parsisolution\Gateway\Transaction::availableStates())
            ->default(\Parsisolution\Gateway\Transaction::STATE_INIT);
        $table->string('ip', 20)->nullable();
        $table->json('extra')->nullable();
        $table->timestamp('paid_at')->nullable();
        $table->nullableTimestamps();
        $table->softDeletes();
    });
}

I THINK - The following section is how I understand the way Laravel work.

Since you are creating your table into the first Schema, you have to put your foreign key into the creation.

The problem is that Laravel Migration will verify that everything will work before applying code, but the stage is the function up(). So everything in it is at the same stage. The migration think that your gateway_transactions doesnt exist, and it doesnt at the moment it verify everything is ok. It will when the code will exist.

Answer 2

The type of the foreign key column must be exactly the same as the reference table.

If the ID of the Users table is a big integer:

$table->bigIncrements('id');

Your foreign key must be:

$table->unsignedBigInteger('user_id');

Then the migration will work correctly.