diff --git a/src/categories/category.entity.ts b/src/categories/category.entity.ts
index 7f8be89..f8332cf 100644
--- a/src/categories/category.entity.ts
+++ b/src/categories/category.entity.ts
@@ -47,7 +47,7 @@ export class Category extends CoreEntity {
 
   @ApiProperty({ description: 'Category Parent ID', example: 1, type: Number })
   @Column({ type: 'int', nullable: true })
-  parentId?: number;
+  parentId?: number | null;
 
   @ManyToOne(() => User, (user) => user.categories, {
     onDelete: 'CASCADE',
diff --git a/src/categories/category.repository.ts b/src/categories/category.repository.ts
index ff6abd9..0e1db69 100644
--- a/src/categories/category.repository.ts
+++ b/src/categories/category.repository.ts
@@ -24,7 +24,7 @@ export class CategoryRepository extends Repository<Category> {
   }
 
   async createOne(
-    category: Category & { parentId?: number },
+    category: Category & { parentId?: number | null },
     entityManager?: EntityManager,
   ): Promise<Category> {
     return entityManager ? entityManager?.save(category) : this.save(category);
diff --git a/src/categories/category.service.ts b/src/categories/category.service.ts
index 03db16d..d7698ec 100644
--- a/src/categories/category.service.ts
+++ b/src/categories/category.service.ts
@@ -244,11 +244,12 @@ export class CategoryService {
       // find children categories
       const childrenCategories = await queryRunnerManager.find(Category, {
         where: { parentId: categoryId },
+        order: { createdAt: 'DESC' },
       });
 
       await queryRunnerManager.save(
         childrenCategories.map((childrenCategory) => {
-          childrenCategory.parentId = parentCategory?.id;
+          childrenCategory.parentId = parentCategory?.id ?? null;
           return childrenCategory;
         }),
       );