diff --git a/PostgreSQL/common.sql b/PostgreSQL/common.sql
index a7956ac..2b04ccd 100644
--- a/PostgreSQL/common.sql
+++ b/PostgreSQL/common.sql
@@ -21,3 +21,19 @@ ALTER DATABASE fortern REFRESH COLLATION VERSION;
 
 REINDEX DATABASE kt_shop;
 ALTER DATABASE kt_shop REFRESH COLLATION VERSION;
+
+-- 重置某表的某列的自增序列 [表名]_[列名]_seq
+ALTER SEQUENCE person_id_seq RESTART WITH 4284858;
+
+-- ctid 会返回一个元组，元组中第一个数字是 page number, 第二个是 slot number。
+select r.ctid, r.* from study.r;
+-- 得到
+-- "(0,1)",1,101
+-- "(0,2)",2,102
+-- "(0,3)",3,103
+
+-- 删除一条
+delete from study.r where id = 2;
+-- 在重新查询，得到
+-- "(0,1)",1,101
+-- "(0,3)",3,103