my changes

database/migrations/2017_07_05_091036_create_collections_table.php

@@ -0,0 +1,36 @@
+<?php
+
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Database\Migrations\Migration;
+
+class CreateCollectionsTable extends Migration
+{
+    /**
+     * Run the migrations.
+     *
+     * @return void
+     */
+    public function up()
+    {
+        Schema::create('collections', function (Blueprint $table) {
+            $table->increments('id');
+            $table->string('number', 255)->nullable();
+            $table->string('name', 255)->nullable();
+            $table->string('oai_subset', 255)->nullable();
+            $table->integer('parent_id')->unsigned()->nullable();
+			$table->foreign('parent_id')->references('id')->on('collections')->onDelete('cascade');
+            $table->boolean('visible')->default('1');
+            $table->timestamps();
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     *
+     * @return void
+     */
+    public function down()
+    {
+        Schema::drop('collections');
+    }
+}