闪加查询、闪回版本查询、闪回事务查询
1.闪回查询：
步骤是记录当前SCN及时间，然后进行DML操作，提交后使用 timestamp和SCN进行对DML操作之前数据的查询
SQL> set time on;
19:13:57 SQL> insert into test select rownum from dual connect by rownum<=5;
5 rows inserted
19:14:47 SQL> commit;
Commit complete
19:14:49 SQL> select dbms_flashback.get_system_change_number from dual;
GET_SYSTEM_CHANGE_NUMBER
------------------------
1362061
19:18:11 SQL> delete test where a>2;
3 rows deleted
19:18:17 SQL> commit;
Commit complete
19:21:56 SQL> select * from test as of timestamp to_timestamp('2013/06/23 19:17:00','yyyy/mm/dd hh24:mi:ss');
A
----------
2
3
4
5
1
19:24:23 SQL> select * from test as of scn 1362061;
A
----------
2
3
4
5
1
2.闪回查询--查询的是已经提交的数据
因为闪回查询的是已经提交的，这样即使数据未提交而
数据库SHUTDOWN ABORT，重启后因为做实例恢复，使用闪回所查询的数据仍是已经提交的。
实验过程：查询当前SCN并执行DML操作不提交并查询当前SCN，使用闪回查询功能查询DML操作之前和之后的SCN
结果是：验证闪回查询返回的是已经提交的数据。
20:22:44 BYS@bys1>select * from test3;
ID NAME
---------- ----------
2 b
20:22:48 BYS@bys1>select current_scn from v$database;
CURRENT_SCN
-----------
1741868
20:26:17 BYS@bys1>delete test3; ---不提交
1 row deleted.
各种查询：
20:26:26 BYS@bys1>select * from test3;
no rows selected
20:26:29 BYS@bys1>select current_scn from v$database;
CURRENT_SCN
-----------
1741881
20:26:50 BYS@bys1>select * from test3 as of scn 1741868;
ID NAME
---------- ----------
2 b
20:27:10 BYS@bys1>select * from test3 as of scn 1741881;
ID NAME
---------- ----------
2 b
3.闪回版本查询
versions_operation: 操作类型
versions_xid: 事务编号
versions_starttime: 开始时间
versions_endtime: 结束时间，如果有值，证明这记录已非当前记录
versions_startscn: 开始SCN号
versions_endscn: 结束SCN号 如果有值，证明这记录已非当前记录
操作步骤：
19:25:28 SQL> select dbms_flashback.get_system_change_number from dual;
GET_SYSTEM_CHANGE_NUMBER
------------------------
1362268
19:37:09 SQL> col versions_starttime for a25
19:37:22 SQL> col versions_endtime for a25
19:38:02 SQL> select versions_startscn,versions_starttime, versions_endtime, versions_operation,versions_xid from test versions between timestampto_timestamp('2013/06/2319:17:00','yyyy/mm/dd hh24:mi:ss')and to_timestamp('2013/06/2319:20:00','yyyy/mm/dd hh24:mi:ss');
VERSIONS_STARTSCN VERSIONS_STARTTIME VERSIONS_ENDTIME VERSIONS_OPERATION VERSIONS_XID
----------------- ------------------------- ------------------------- ------------------ ----------------
1362122 23-JUN-13 07.19.48 PM D 04001200C8020000
1362122 23-JUN-13 07.19.48 PM D 04001200C8020000
1362122 23-JUN-13 07.19.48 PM D 04001200C8020000
23-JUN-13 07.19.48 PM
23-JUN-13 07.19.48 PM
23-JUN-13 07.19.48 PM
8 rows selected
4.闪回事务查询
闪回事务查询需要打开追加日志，不然无法从 flashback_transaction_query查出UNDO_SQL
20:35:42 SQL> show parameter undo
NAME TYPE VALUE
------------------------------------ ----------- --