diff --git a/troubleshooting/250918_gmail_token_slack_user_id_column_missing.md b/troubleshooting/250918_gmail_token_slack_user_id_column_missing.md
index 0d59f68..02e53ac 100644
--- a/troubleshooting/250918_gmail_token_slack_user_id_column_missing.md
+++ b/troubleshooting/250918_gmail_token_slack_user_id_column_missing.md
@@ -52,5 +52,24 @@ if creds and creds.expired and creds.refresh_token:
 - `refresh_token` 존재 여부
 - Google OAuth 설정 확인
 
+## 해결 방법
+
+### 수정 필요 파일
+`/home/admin/ivada_project/skill_email/services/db_credentials_provider.py`
+- 68번 줄: get_credentials()
+- 170번 줄: save_credentials()
+- 234번 줄: has_equipped_token()
+
+### 수정 내용
+```python
+# 기존 (잘못됨)
+WHERE slack_user_id = %s
+
+# 수정 (JOIN 사용)
+FROM gmail_token gt
+JOIN user u ON gt.user_id = u.id
+WHERE u.oauth_id = %s
+```
+
 ## 관련 문서
 - [250831_skill-email_UUID_inconsistency_URGENT.md](./250831_happybell80_skill-email_UUID_inconsistency_URGENT.md)
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