mydb=# create table num(
mydb(# id int,
mydb(# value int);
CREATE TABLE
mydb=# insert into num values (1,17),(2,68),(3,-34);
INSERT 0 3
mydb=# select * from num;
 id | value
----+-------
  1 |    17
  2 |    68
  3 |   -34
(3 rows)

mydb=# begin;
BEGIN
mydb=# savepoint m;
SAVEPOINT
mydb=# update num set value=9;
UPDATE 3
mydb=# select * from num;
 id | value
----+-------
  1 |     9
  2 |     9
  3 |     9
(3 rows)

mydb=# roolback to m;
ERROR:  syntax error at or near "roolback"
LINE 1: roolback to m;
        ^
mydb=# rollback to m;
ROLLBACK
mydb=# select * from num;
 id | value
----+-------
  1 |    17
  2 |    68
  3 |   -34
(3 rows)

mydb=# commit;
COMMIT
mydb=#

update num set value=9;
這個例子中不小心寫錯了一個語句導致表中每條記錄的value字段都被改成了9
然後使用rollback撤銷了這個操作，數據表恢復正常。