increments('id'); $table->integer('user_id')->unsigned()->index(); $table->integer('artist_id')->unsigned()->nullable()->index(); $table->integer('playlist_id')->unsigned()->nullable()->index(); $table->timestamp('created_at'); $table->foreign('user_id')->references('id')->on('users')->on_delete('cascade'); $table->foreign('artist_id')->references('id')->on('users')->on_delete('cascade'); $table->foreign('playlist_id')->references('id')->on('playlists'); }); } public function down() { Schema::drop('followers'); } }