laravel 8 "Foreign key constraint is incorrectly formed" code example

Example 1: errno: 150 foreign key constraint is incorrectly formed laravel 8

Since increments() creates an unsigned integer column, you need to define the foreign key column as unsigned integer too.

Default migrations in Laravel 6+ use bigIncrements(), so you need to use unsignedBigInteger() method:

$table->unsignedBigInteger('order_id');
https://laravel.com/docs/6.x/migrations#foreign-key-constraints

For default migrations in older versions of Laravel use unsignedInteger() method:

$table->unsignedInteger('order_id');
Or:

$table->integer('order_id')->unsigned();

Example 2: foreign key constraint is incorrectly formed laravel

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');