Flashback Query 

you must choose an undo retention interval that is long enough to enable users to construct a snapshot of the database for the oldest version of the database that they are interested in.


SQL> conn sys as sysdba
Enter password:
Connected.
SQL> alter system set undo_retention = 3600;
System altered.
SQL> conn hr/hr
Connected.
SQL> alter session set nls_date_format = 'hh24:mi:ss';
Session altered.
SQL> select sysdate from dual;
SYSDATE
--------
19:04:49
SQL> create table hrtest ( no number, name varchar2(20));
Table created.
SQL> begin
2 insert into hrtest values ( 1, 'aaa');
3 insert into hrtest values ( 2, 'bbb');
4 insert into hrtest values ( 3, 'ccc');
5 end;
6 /
PL/SQL procedure successfully completed.
SQL> commit;
Commit complete.
SQL> select sysdate from dual;
SYSDATE
--------
19:06:23
SQL> delete from hrtest where name = 'ccc';
1 row deleted.
SQL> commit;
Commit complete.
SQL> select * from hrtest;
NO NAME
---------- --------------------
1 aaa
2 bbb

SQL> edWrote file afiedt.buf
1 select * from hrtest AS OF TIMESTAMP 2 to_timestamp ('2006-11-16 19:06:23','YYYY-MM-DD HH24:MI:SS')
3* where name = 'ccc'
4 /
NO NAME
---------- --------------------
3 ccc
SQL> insert into hrtest 2 ( select * from hrtest AS OF TIMESTAMP 3 to_timestamp ('2006-11-16 19:06:23','YYYY-MM-DD HH24:MI:SS')
4 where name = 'ccc');
1 row created.
SQL> select * from hrtest;
NO NAME
---------- --------------------
1 aaa
2 bbb
3 ccc