diff --git a/PostgreSQL/prism/prism.sql b/PostgreSQL/prism/prism.sql
index ff9f080..1dcdef3 100644
--- a/PostgreSQL/prism/prism.sql
+++ b/PostgreSQL/prism/prism.sql
@@ -6,6 +6,9 @@ from activities;
 select to_timestamp(min(timestamp))
 from activities;
 
+-- 数据总量
+select max(activity_id) - min(activity_id) + 1 from activities;
+
 -- 1天内的数据，按action分组排序
 select b.action_id, b.action, count(b.action_id)
 from activities as a