diff --git a/backend/sql/002b_migrate_episode_number.sql b/backend/sql/002b_migrate_episode_number.sql
new file mode 100644
index 0000000..0a69304
--- /dev/null
+++ b/backend/sql/002b_migrate_episode_number.sql
@@ -0,0 +1,18 @@
+-- ============================================================
+-- 002b_migrate_episode_number.sql
+-- 迁移脚本：在 002a 诊断确认安全后执行
+-- 执行方式: psql -U postgres -d milsci_dev -f sql/002b_migrate_episode_number.sql
+-- 前置条件：先设 $env:PGCLIENTENCODING="UTF8"
+-- 注意：已改用 date_part('year', air_date) 替代 EXTRACT(... )::int 避免语法错误
+-- ============================================================
+
+-- 1. 删全局 UNIQUE 约束（幂等：constraint 已删则报 warning，正常）
+ALTER TABLE episodes DROP CONSTRAINT episodes_episode_number_key;
+
+-- 2. 建按年复合唯一索引（重播行 original_episode_id IS NOT NULL 不参与）
+CREATE UNIQUE INDEX idx_episodes_year_number
+  ON episodes (date_part('year', air_date), episode_number)
+  WHERE original_episode_id IS NULL;
+
+-- 验证：确认索引生效
+-- \d episodes
\ No newline at end of file
diff --git a/backend/sql/002c_recreate_index_only.sql b/backend/sql/002c_recreate_index_only.sql
new file mode 100644
index 0000000..7d5db10
--- /dev/null
+++ b/backend/sql/002c_recreate_index_only.sql
@@ -0,0 +1,10 @@
+-- ============================================================
+-- 002c_recreate_index_only.sql
+-- 002b 跑半截翻车后补救：只执行 CREATE INDEX，不要再 DROP CONSTRAINT
+-- 执行方式: psql -U postgres -d milsci_dev -f sql/002c_recreate_index_only.sql
+-- 前置条件：先设 $env:PGCLIENTENCODING="UTF8"
+-- ============================================================
+
+CREATE UNIQUE INDEX idx_episodes_year_number
+  ON episodes (date_part('year', air_date), episode_number)
+  WHERE original_episode_id IS NULL;
\ No newline at end of file