[FIXED] Laravel 5.4: SQLSTATE[HY000]: General error: 1005 Can't create table "Foreign key constraint is incorrectly formed"

Issue

I'm using Laravel 5.4 and I have added this Migration:

public function up()
    {
        Schema::create('episodes', function (Blueprint $table) {
            $table->increments('id');
            $table->integer('course_id')->unsigned();
            $table->foreign('course_id')->references('id')->on('courses')->onDelete('cascade');
            $table->string('type', 10);
            $table->string('title');
            $table->string('slug');
            $table->text('description');
            $table->text('body');
            $table->string('videoUrl');
            $table->string('tags');
            $table->string('time', 15)->default('00:00:00');
            $table->integer('number');
            $table->integer('viewCount')->default(0);
            $table->integer('commentCount')->default(0);
            $table->integer('downloadCount')->default(0);
            $table->timestamps();
        });
    }

Now when I run php artisan migrate, I get this error:

SQLSTATE[HY000]: General error: 1005 Can't create table elearning.episodes (errno: 150 "Foreign key constraint is incorrectly formed") (SQL: alter table episodes add constraint episodes_course_id_foreign foreign key (course_id) references courses (id) on delete cascade)

I also tried this but still gets the same error:

$table->unsignedBigInteger('course_id');

So how can I properly run this Migration? I'm really stuck with this, please help me out...

---

USERS MIGRATTION:

Schema::create('users', function (Blueprint $table) {
            $table->increments('id');
            $table->string('level')->default('user');
            $table->string('name');
            $table->string('email')->unique();
            $table->string('password');
            $table->rememberToken();
            $table->timestamps();
        });

Course Migration:

Schema::create('courses', function (Blueprint $table) {
            $table->increments('id');
            $table->integer('user_id')->unsigned();
            $table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');
            $table->string('type', 10);
            $table->string('title');
            $table->string('slug');
            $table->text('description');
            $table->text('body');
            $table->string('price',50);
            $table->string('imageUrl');
            $table->string('tags');
            $table->string('time', 15)->default('00:00:00');
            $table->integer('viewCount')->default(0);
            $table->integer('commentCount')->default(0);
            $table->timestamps();
        });

Solution

Rather than use :

$table->increments('id');

you should use :

$table->id();

(it's just easier).

To create your foreign relationships, rather than have

$table->integer('course_id')->unsigned();
$table->foreign('course_id')->references('id')->on('courses')->onDelete('cascade');

you can just use :

$table->foreignId('course_id')->constrained()->cascadeOnDelete();

which will automatically create a column of the right type (unsigned big integer) and then create the relationship by looking for the id column on the courses table.

EDIT

As you're using an older version of Laravel, you cannot use the id() function, so just create the course_id column as a big integer :

$table->bigInteger('course_id')->unsigned();

and then create your relationship as before.

Answered By - Giles Bennett