diff --git a/note.md b/note.md
index 13f37ca0..2b052563 100644
--- a/note.md
+++ b/note.md
@@ -287,4 +287,19 @@ mysql> EXPLAIN SELECT c.id, c.name, c.political_party, c.sex, v.count
 |  1 | PRIMARY     | <derived2> | NULL       | ref   | <auto_key0>            | <auto_key0>            | 4       | ishocon2.c.id |   128 |   100.00 | NULL                            |
 |  2 | DERIVED     | votes      | NULL       | index | idx_votes_candidate_id | idx_votes_candidate_id | 4       | NULL          | 12863 |   100.00 | NULL                            |
 +----+-------------+------------+------------+-------+------------------------+------------------------+---------+---------------+-------+----------+---------------------------------+
+```
+
+- add foreign key to votes to candidates 28840
+
+```
+❯ make bench
+docker exec -i ishocon2-bench-1 sh -c "./benchmark --ip app:443 --workload 6"
+2024/01/02 04:26:26 Start GET /initialize
+2024/01/02 04:26:26 期日前投票を開始します
+2024/01/02 04:26:27 期日前投票が終了しました
+2024/01/02 04:26:27 投票を開始します  Workload: 6
+2024/01/02 04:27:13 投票が終了しました
+2024/01/02 04:27:13 投票者が結果を確認しています
+2024/01/02 04:27:28 投票者の感心がなくなりました
+2024/01/02 04:27:28 {"score": 28840, "success": 26120, "failure": 0}
 ```
\ No newline at end of file
diff --git a/webapp/ruby/app.rb b/webapp/ruby/app.rb
index 94c0e05a..e422c96f 100644
--- a/webapp/ruby/app.rb
+++ b/webapp/ruby/app.rb
@@ -96,6 +96,7 @@ def db_initialize
       db.query('DELETE FROM votes')
       db.query('ALTER TABLE votes ADD INDEX idx_votes_candidate_id (candidate_id)')
       db.query('ALTER TABLE votes ADD COLUMN count int(4) NOT NULL')
+      db.query('ALTER TABLE votes ADD CONSTRAINT fk_votes_to_candidate FOREIGN KEY (candidate_id) REFERENCES candidates (id)')
     end
   end