diff --git a/backend/src/main/java/com/xly/erp/module/mod/mapper/ModuleMapper.java b/backend/src/main/java/com/xly/erp/module/mod/mapper/ModuleMapper.java
index 15001f6..2464d1f 100644
--- a/backend/src/main/java/com/xly/erp/module/mod/mapper/ModuleMapper.java
+++ b/backend/src/main/java/com/xly/erp/module/mod/mapper/ModuleMapper.java
@@ -13,4 +13,7 @@ public interface ModuleMapper extends BaseMapper<Module> {
     default boolean existsActiveById(Integer iIncrement) {
         return findActiveFlagById(iIncrement) != null;
     }
+
+    @Select("SELECT iParentId FROM tModule WHERE iIncrement = #{id} AND bDeleted = 0")
+    Integer selectParentIdById(@Param("id") Integer iIncrement);
 }
diff --git a/backend/src/test/java/com/xly/erp/module/mod/mapper/ModuleMapperIT.java b/backend/src/test/java/com/xly/erp/module/mod/mapper/ModuleMapperIT.java
index 3dc888a..527b31b 100644
--- a/backend/src/test/java/com/xly/erp/module/mod/mapper/ModuleMapperIT.java
+++ b/backend/src/test/java/com/xly/erp/module/mod/mapper/ModuleMapperIT.java
@@ -60,6 +60,24 @@ class ModuleMapperIT {
         assertThat(moduleMapper.existsActiveById(99999999)).isFalse();
     }
 
+    @Test
+    void selectParentIdById_returnsNullForRootOrMissing_andValueForChild() {
+        Module root = newModule("sp_test_root", "根", null);
+        moduleMapper.insert(root);
+
+        Module child = newModule("sp_test_child", "子", root.getIIncrement());
+        moduleMapper.insert(child);
+
+        Module deleted = newModule("sp_test_del", "删", root.getIIncrement());
+        deleted.setBDeleted(true);
+        moduleMapper.insert(deleted);
+
+        assertThat(moduleMapper.selectParentIdById(root.getIIncrement())).isNull();
+        assertThat(moduleMapper.selectParentIdById(child.getIIncrement())).isEqualTo(root.getIIncrement());
+        assertThat(moduleMapper.selectParentIdById(deleted.getIIncrement())).isNull();
+        assertThat(moduleMapper.selectParentIdById(99999998)).isNull();
+    }
+
     private Module newModule(String procedureName, String nameZh, Integer parentId) {
         Module m = new Module();
         m.setSBrandsId("XLY");