diff --git a/example/fixture.py b/example/fixture.py
index 2d99852..6958161 100644
--- a/example/fixture.py
+++ b/example/fixture.py
@@ -1,11 +1,34 @@
 from typing import Any
 
+from .models.category import Category
 from .models.group import Group
 from .models.user import User
 
 
 def get_data() -> dict[str, dict[int, Any]]:
     return {
+        "categories": {
+            1: Category(
+                id=1,
+                name="First category",
+                parent_id=None,
+            ),
+            2: Category(
+                id=2,
+                name="Second category",
+                parent_id=None,
+            ),
+            3: Category(
+                id=3,
+                name="Child category",
+                parent_id=1,
+            ),
+            4: Category(
+                id=4,
+                name="Other child category",
+                parent_id=1,
+            ),
+        },
         "groups": {
             1: Group(
                 id=1,
diff --git a/example/models/category.py b/example/models/category.py
new file mode 100644
index 0000000..21db613
--- /dev/null
+++ b/example/models/category.py
@@ -0,0 +1,8 @@
+from dataclasses import dataclass
+
+
+@dataclass
+class Category:
+    id: int
+    name: str
+    parent_id: int | None
diff --git a/example/queries/__init__.py b/example/queries/__init__.py
index 07f0b0a..546fb50 100644
--- a/example/queries/__init__.py
+++ b/example/queries/__init__.py
@@ -1,8 +1,9 @@
 from typing import Any
 
-from . import groups, hello, users
+from . import categories, groups, hello, users
 
 queries: Any = [
+    categories.Query,
     groups.Query,
     hello.Query,
     users.Query,
diff --git a/example/queries/categories.py b/example/queries/categories.py
new file mode 100644
index 0000000..bbff01f
--- /dev/null
+++ b/example/queries/categories.py
@@ -0,0 +1,22 @@
+from ariadne_graphql_modules import GraphQLObject
+from graphql import GraphQLResolveInfo
+
+from ..database import db
+from ..types.category import CategoryType
+
+
+class Query(GraphQLObject):
+    @GraphQLObject.field()
+    @staticmethod
+    async def categories(obj, info: GraphQLResolveInfo) -> list[CategoryType]:
+        return await db.get_all("categories", parent_id=None)
+
+    @GraphQLObject.field()
+    @staticmethod
+    async def category(obj, info: GraphQLResolveInfo, id: str) -> CategoryType | None:
+        try:
+            id_int = int(id)
+        except (TypeError, ValueError):
+            return None
+
+        return await db.get_row("categories", id=id_int)
diff --git a/example/types/category.py b/example/types/category.py
new file mode 100644
index 0000000..24d2731
--- /dev/null
+++ b/example/types/category.py
@@ -0,0 +1,36 @@
+from ariadne_graphql_modules import GraphQLObject
+from ariadne import gql
+from graphql import GraphQLResolveInfo
+
+from ..database import db
+from ..models.category import Category
+
+
+class CategoryType(GraphQLObject):
+    __schema__ = gql(
+        """
+        type Category {
+            id: ID!
+            name: String!
+            parent: Category
+            children: [Category!]!
+        }
+        """
+    )
+
+    @GraphQLObject.resolver("parent", "CategoryType")
+    @staticmethod
+    async def resolve_parent(
+        obj: Category, info: GraphQLResolveInfo
+    ) -> Category | None:
+        if not obj.parent_id:
+            return None
+
+        return await db.get_row("categories", id=obj.parent_id)
+
+    @GraphQLObject.resolver("children", list["CategoryType"])
+    @staticmethod
+    async def resolve_children(
+        obj: Category, info: GraphQLResolveInfo
+    ) -> list[Category]:
+        return await db.get_all("categories", parent_id=obj.id)