Laravel migration: "Foreign key constraint is incorrectly formed" (errno 150)

When migrating my DB, this error appears. Below is my code followed by the error that I am getting when trying to run the migration.

Code

public function up()
{
    Schema::create('meals', function (Blueprint $table) {
        $table->increments('id');
        $table->integer('user_id')->unsigned();
        $table->integer('category_id')->unsigned();
        $table->string('title');
        $table->string('body');
        $table->string('meal_av');
        $table->timestamps();
        $table->foreign('user_id')
            ->references('id')
            ->on('users')
            ->onDelete('cascade');
        $table->foreign('category_id')
            ->references('id')
            ->on('categories')
            ->onDelete('cascade');
    });
}  

Error message

[Illuminate\Database\QueryException]
SQLSTATE[HY000]: General error: 1005 Can't create table meal.#sql-11d2_1 4 (errno: 150 "Foreign key constraint is incorrectly formed") (SQL: alter
table meals add constraint meals_category_id_foreign foreign key (category_id) references categories (id) on delete cascade)

When creating a new table in Laravel. A migration will be generated like:

$table->bigIncrements('id');

Instead of (in older Laravel versions):

$table->increments('id');

When using bigIncrements the foreign key expects a bigInteger instead of an integer. So your code will look like this:

public function up()
    {
        Schema::create('meals', function (Blueprint $table) {
            $table->increments('id');
            $table->unsignedBigInteger('user_id'); //changed this line
            $table->unsignedBigInteger('category_id'); //changed this line
            $table->string('title');
            $table->string('body');
            $table->string('meal_av');
            $table->timestamps();

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

            $table->foreign('category_id')
                ->references('id')
                ->on('categories')
                ->onDelete('cascade');
        });
    }  

You could also use increments instead of bigIncrements like Kiko Sejio said.

The difference between Integer and BigInteger is the size:

• int => 32-bit
• bigint => 64-bit

@JuanBonnett’s question has inspired me to find the answer. I used Laravel to automate the process without considering the creation time of the file itself. According to the workflow, “meals” will be created before the other table (categories) because I created its schema file (meals) before categories. That was my fault.

Just add ->unsigned()->index() at the end of the foreign key and it will work.

You should create your migration in order for example I want my users to have a role_id field which is from my roles table

I first start to make my role migration php artisan make:migration create_roles_table --create=roles

then my second user migration php artisan make:migration create_users_table --create=users

php artisan migration will execute using the order of the created files 2017_08_22_074128_create_roles_table.php and 2017_08_22_134306_create_users_table check the datetime order, that will be the execution order.

files 2017_08_22_074128_create_roles_table.php

public function up()
{
    Schema::create('roles', function (Blueprint $table) {
        $table->increments('id');
        $table->string('name', 50);
        $table->timestamps();
    });
}

2017_08_22_134306_create_users_table

public function up()
{
    Schema::create('users', function (Blueprint $table) {
        $table->increments('id');
        $table->integer('role_id')->unsigned();
        $table->string('name');
        $table->string('phone', 20)->unique();
        $table->string('password');
        $table->rememberToken();
        $table->boolean('active');
        $table->timestamps();
        $table->foreign('role_id')->references('id')->on('roles');
    });
}