diff --git a/htykc_models/migrations/2026-04-27-100000_add_clazz_completed_at/up.sql b/htykc_models/migrations/2026-04-27-100000_add_clazz_completed_at/up.sql
index b3b59fd..6ccc9f2 100644
--- a/htykc_models/migrations/2026-04-27-100000_add_clazz_completed_at/up.sql
+++ b/htykc_models/migrations/2026-04-27-100000_add_clazz_completed_at/up.sql
@@ -1,7 +1,7 @@
 -- 业务「已结课」：首次点名落库时间；清空出勤后回到 NULL。与 start_from/end_by 日历态互补。
 
 ALTER TABLE clazz
-    ADD COLUMN completed_at TIMESTAMP NULL;
+    ADD COLUMN IF NOT EXISTS completed_at TIMESTAMP NULL;
 
 COMMENT ON COLUMN clazz.completed_at IS
     '首次批量保存出勤且存在有效行时写入；出勤被清空则置 NULL。NULL 表示业务上未结课。';