diff --git a/app/Models/OrderRefundTask.php b/app/Models/OrderRefundTask.php
index e77d066b..486253a5 100644
--- a/app/Models/OrderRefundTask.php
+++ b/app/Models/OrderRefundTask.php
@@ -19,10 +19,27 @@ class OrderRefundTask extends Model
      * @var array
      */
     protected $fillable = [
+        'sn',
         'order_id',
         'after_sale_id',
         'amount',
         'status',
         'failed_reason',
     ];
+
+    /**
+     * 只查询待退款的任务
+     */
+    public function scopePending($query)
+    {
+        return $query->where('status', static::STATUS_PENDING);
+    }
+
+    /**
+     * 此退款任务所属的订单
+     */
+    public function order()
+    {
+        return $this->belongsTo(Order::class);
+    }
 }
diff --git a/database/migrations/2021_12_20_113756_create_order_refund_tasks_table.php b/database/migrations/2021_12_20_113756_create_order_refund_tasks_table.php
index 523669e8..ea67b41b 100644
--- a/database/migrations/2021_12_20_113756_create_order_refund_tasks_table.php
+++ b/database/migrations/2021_12_20_113756_create_order_refund_tasks_table.php
@@ -15,6 +15,7 @@ class CreateOrderRefundTasksTable extends Migration
     {
         Schema::create('order_refund_tasks', function (Blueprint $table) {
             $table->id();
+            $table->string('sn')->comment('退款单号');
             $table->unsignedBigInteger('order_id')->comment('订单ID');
             $table->unsignedBigInteger('after_sale_id')->nullable()->comment('售后ID');
             $table->unsignedBigInteger('amount')->comment('退款金额');
@@ -22,6 +23,7 @@ class CreateOrderRefundTasksTable extends Migration
             $table->string('failed_reason')->nullable()->comment('失败原因');
             $table->timestamps();
 
+            $table->unique('sn');
             $table->unique(['order_id', 'after_sale_id']);
         });
     }