diff --git a/update_db.py b/update_db.py
index b83127d..ea69a45 100644
--- a/update_db.py
+++ b/update_db.py
@@ -26,10 +26,10 @@ def main (
 
 
 def update_video_table (
-        video_dao,
+        video_dao:  VideoDao,
         api_data:   list[dict],
 ) -> None:
-    # TODO: 書くこと
+    # TODO: videos 取得書くこと
 
     video_dao.upsert_all (videos)
 
@@ -176,7 +176,7 @@ class VideoDao:
             self,
             videos:                 list[VideoDto],
             with_relation_tables:   bool            = True,
-    ) -> int:
+    ) -> None:
         with self.conn.cursor () as c:
             for video in videos:
                 c.execute ("""
@@ -199,14 +199,16 @@ class VideoDao:
                           title = VALUES(title),
                           description = VALUES(description),
                           uploaded_at = VALUES(uploaded_at),
-                          deleted_at = VALUES(deleted_at)""", (
-                               video.code,
-                               video.title,
-                               video.description,
-                               video.uploaded_at,
-                               video.deleted_at))
+                          deleted_at = VALUES(deleted_at)""", (video.code,
+                                                               video.title,
+                                                               video.description,
+                                                               video.uploaded_at,
+                                                               video.deleted_at))
                 video.id_ = c.lastrowid
-                # TODO: with_relation_tables が True の場合，子テーブルも UPSERT すること
+                if with_relation_tables:
+                    VideoTagDao (self.conn).upsert_all (video.video_tags, False)
+                    CommentDao (self.conn).upsert_all (video.comments, False)
+                    VideoHistoryDao (self.conn).upsert_all (video.video_histories, False)
 
     def _create_dto_from_row (
             self,
@@ -218,10 +220,7 @@ class VideoDao:
                           title           = row['title'],
                           description     = row['description'],
                           uploaded_at     = row['uploaded_at'],
-                          deleted_at      = row['deleted_at'],
-                          video_tags      = None,
-                          comments        = None,
-                          video_histories = None)
+                          deleted_at      = row['deleted_at'])
         if with_relation_tables:
             video.video_tags = VideoTagDao (self.conn).fetch_by_video_id (video.id_, False)
             for i in range (len (video.video_tags)):
@@ -237,15 +236,15 @@ class VideoDao:
 
 @dataclass (slots = True)
 class VideoDto:
-    id_:                int
+    id_:                int | None                      = None
     code:               str
     title:              str
     description:        str
     uploaded_at:        datetime
-    deleted_at:         datetime | None
-    video_tags:         list[VideoTagDto] | None
-    comments:           list[CommentDto] | None
-    video_histories:    list[VideoHistoryDto] | None
+    deleted_at:         datetime | None                 = None
+    video_tags:         list[VideoTagDto] | None        = None
+    comments:           list[CommentDto] | None         = None
+    video_histories:    list[VideoHistoryDto] | None    = None
 
 
 class VideoTagDao:
@@ -288,9 +287,7 @@ class VideoTagDao:
                                  video_id       = row['video_id'],
                                  tag_id         = row['tag_id'],
                                  tagged_at      = row['tagged_at'],
-                                 untagged_at    = row['untagged_at'],
-                                 video          = None,
-                                 tag            = None)
+                                 untagged_at    = row['untagged_at'])
         if with_relation_tables:
             video_tag.video = VideoDao (self.conn).fetch (video_tag.video_id, True)
             video_tag.tag = TagDao (self.conn).fetch (video_tag.tag_id, True)
@@ -299,13 +296,13 @@ class VideoTagDao:
 
 @dataclass (slots = True)
 class VideoTagDto:
-    id_:            int
+    id_:            int | None      = None
     video_id:       int
     tag_id:         int
     tagged_at:      datetime
     untagged_at:    datetime
-    video:          VideoDto
-    tag:            TagDto
+    video:          VideoDto | None = None
+    tag:            TagDto | None   = None
 
 
 if __name__ == '__main__':