Cannot add foreign key constraint on vps server

Question

so I use my project locally and run this code php artisan migrate everything works perfectly fine and my tables will be created

but when I move to my vps and do the same thing I get this error

[Illuminate\\Database\\QueryException] SQLSTATE[HY000]: General error: 1215 Cannot add foreign key constraint (SQL : alter table mediables add constraint mediables_media_id_foreign forei gn key ( media_id ) references media ( id ) on delete cascade)

I followed some solution from this site but they didn't work

my migration file :

 Schema::create('media', function (Blueprint $table) {
        $table->increments('id');
        $table->string('name')->nullable();
        $table->string('old_name')->nullable();
        $table->text('desc')->nullable();
        $table->string('category')->nullable();
        $table->string('type');
        $table->string('format');
        $table->string('href');
        $table->string('thumbnail')->nullable();

        $table->timestamps();
    });

    Schema::create('mediables', function (Blueprint $table) {

        $table->integer('media_id')->nullable();
        $table->integer('mediable_id');
        $table->string('mediable_type');
        $table->primary(['media_id','mediable_id','mediable_type']);

        $table->timestamps();
    });
    Schema::table('mediables', function (Blueprint $table) {
        $table->foreign('media_id')
            ->references('id')->on('media')
            ->onDelete('cascade');
    });

note that there is a polymorphic relation between media and other models in my project

the only difference between my local machine and my vps is that I have apache locally and nginx on vps if it's related

Answer 1

media table should have id column, because media_id references to it.

Also, if id is increment() , you should use unsigned() foreign key:

$table->integer('media_id')->unsigned()->nullable();

Answer 2

if you're using new WAMP take care of it's mysql as it's by default will accept any relation even between non-existing columns like

$table->foreign('media_id')
        ->references('id')->on('media')
        ->onDelete('cascade');

the id isn't existing in media table.

Also $table->primary(['media_id','mediable_id','mediable_type']); won't run as you've already set a primary id as $table->increments('id'); will set id as a primary.

Answer 3

You have to set table engine to InnoDB by default or set it explicitly with

$table->engine = 'InnoDB';

Only the InnoDB engine handles foreign key constraints.