update

app/Models/User.php

@@ -209,14 +209,13 @@ class User extends Authenticatable implements Auditable
                 ->whereIn('course_id', $course->pluck('id'))
                 ->selectRaw('MIN(id)')
                 ->groupBy('user_id');
-        })->whereHas('user', function ($query) {
-            $query->whereNull('no');
         })->orderBy('created_at', 'asc')->get();
+
         // 获取当前用户id在$courseSigns中第几位
         $index = $courseSigns->search(function ($item) use ($user) {
             return $item->user_id == $user->id;
         });
-        $no = $prefix . str_pad($index, 3, '0', STR_PAD_LEFT);
+        $no = $prefix . str_pad($index + 1, 3, '0', STR_PAD_LEFT);
         $user->no = $no;
         $user->save();
         return $user->no;