SQLite vs MySQL - foreign key checks

Sqlite does not check for foreign key integrity when creating tables, only when inserting records. However, MySQL does check in both cases.

To make this more clear, let's take a look at a simple example: given two tables - todos and users - created in this **exact order**:

```php
 Schema::create('todos', function (Blueprint $table) {
      $table->id();
      $table->string('title');
      $table->unsignedBigInteger('user_id');
      $table->foreign('user_id')
          ->references('id')
          ->on('users');
  });
```

```php
 Schema::create('users', function (Blueprint $table) {
      $table->id();
      $table->string('username');
      $table->string('password');
  });
```
If you run your migrations using the `sqlite` driver, everything works just fine.

However, if you run your migrations using the `mysql` driver, you get the following error:

```sql
SQLSTATE[HY000]: General error: 1005 Can't create table `[your-app]`.`todos` 
(errno: 150 "Foreign key constraint is incorrectly formed") 
(SQL: alter table `todos` add constraint `todos_user_id_foreign`
 foreign key (`user_id`) references `users` (`id`))
```

Denisa Halmaghi
26 Nov 2021