diff --git a/migrations/003_post_cover_image.sql b/migrations/003_post_cover_image.sql
new file mode 100644
index 0000000..5d650d2
--- /dev/null
+++ b/migrations/003_post_cover_image.sql
@@ -0,0 +1,5 @@
+-- 新增封面图字段
+ALTER TABLE posts ADD COLUMN cover_image VARCHAR(500);
+
+-- 为封面图添加索引
+CREATE INDEX idx_posts_cover ON posts(cover_image) WHERE cover_image IS NOT NULL;