add exam index init value

database/migrations/2021_06_11_014259_create_exam_index_init_values_table.php

@@ -0,0 +1,37 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+class CreateExamIndexInitValuesTable extends Migration
+{
+    /**
+     * Run the migrations.
+     *
+     * @return void
+     */
+    public function up()
+    {
+        Schema::create('exam_index_init_values', function (Blueprint $table) {
+            $table->id();
+            $table->integer('uid')->index();
+            $table->integer('exam_user_id');
+            $table->integer('exam_id')->index();
+            $table->integer('index')->index();
+            $table->bigInteger('value');
+            $table->timestamps();
+            $table->unique(['exam_user_id', 'exam_id', 'index']);
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     *
+     * @return void
+     */
+    public function down()
+    {
+        Schema::dropIfExists('exam_index_init_values');
+    }
+}