update

app/Http/Controllers/Admin/CalendarsController.php

@@ -50,7 +50,7 @@ class CalendarsController extends BaseController
     public function index()
     {
         $all = \request()->all();
-        $list = Calendar::with('course', 'courseContent')
+        $list = Calendar::with('course', 'courseContent','historyCourses')
             ->where(function ($query) use ($all) {
                 if (isset($all['month'])) {
                     $query->where('start_time', 'like', $all['month'] . '%');

app/Models/Calendar.php

@@ -44,7 +44,7 @@ class Calendar extends SoftDeletesModel
 
     public function historyCourses()
     {
-        return $this->hasMany(HistoryCourse::class, 'calendar_id', 'id');
+        return $this->hasOne(HistoryCourse::class, 'calendar_id', 'id');
     }
 
 }