diff --git a/PostgreSQL/prism/prism.sql b/PostgreSQL/prism/prism.sql
index ef92905..64db4df 100644
--- a/PostgreSQL/prism/prism.sql
+++ b/PostgreSQL/prism/prism.sql
@@ -1,9 +1,9 @@
 -- 获取最新的数据
-select max(timestamp)
+select to_timestamp(max(timestamp))
 from activities;
 
 -- 获取最旧的数据
-select min(timestamp)
+select to_timestamp(min(timestamp))
 from activities;
 
 -- 1天内的数据，按action分组排序