oracle的闪回查询，闪回删除：

create table t1 as select * from dba_objects;
SCOTT@ORA12C> select sysdate from dual;
SYSDATE
-------------------
2015-09-20 14:54:10
1 row selected.
SCOTT@ORA12C> delete from t1;
0 rows deleted.
SCOTT@ORA12C> commit;
Commit complete.
SCOTT@ORA12C> select count(*) from t1;

COUNT(*)
-----------------
0
1 row selected.
SCOTT@ORA12C> select count(*) from t1 as of timestamp to_timestamp('2015-09-20 14:54:00','yyyy-mm-dd hh24:mi:ss');
COUNT(*)
-----------------
91692
1 row selected.
SCOTT@ORA12C> flashback table t1 to timestamp to_timestamp('2015-09-20 14:54:00','yyyy-mm-dd hh24:mi:ss');
flashback table t1 to timestamp to_timestamp('2015-09-20 14:54:00','yyyy-mm-dd hh24:mi:ss') *
ERROR at line 1:
ORA-08189: cannot flashback the table because row movement is not enabled
SCOTT@ORA12C> alter table t1 enable row movement;
Table altered.
SCOTT@ORA12C> flashback table t1 to timestamp to_timestamp('2015-09-20 14:54:00','yyyy-mm-dd hh24:mi:ss');
Flashback complete.
SCOTT@ORA12C> select count(*) from t1;
COUNT(*)
-----------------
91692

1 row selected.
注意system表空间下面的表不能闪回，不能跨越DDL语句，

SYS@ORA12C> flashback table t2 to timestamp to_timestamp('2015-09-20 15:07:25','yyyy-mm-dd hh24:mi:ss');
flashback table t2 to timestamp to_timestamp('2015-09-20 15:07:25','yyyy-mm-dd hh24:mi:ss') *
ERROR at line 1:
ORA-08185: Flashback not supported for user SYS
但是可以查询：
SYS@ORA12C> select count(*) from t2 as of timestamp to_timestamp('2015-09-20 15:07:25','yyyy-mm-dd hh24:mi:ss');

COUNT(*)
-----------------
91694
1 row selected.
可以重新建一张表或者直接insert：
SYS@ORA12C> create table t3 as select * from t2 as of timestamp to_timestamp('2015-09-20 15:07:25','yyyy-mm-dd hh24:mi:ss');
Table created.
SYS@ORA12C> insert into t2 select * from t2 as of timestamp to_timestamp('2015-09-20 15:07:25','yyyy-mm-dd hh24:mi:ss');
91694 rows created.
@ORA12C> commit;

Commit complete.