Oracle 11g闪回flashback oracle9i的闪回： 闪回查询从9i引入，可以按照时间点或者SCN向前查 询，获取修改 前的数据。
Oracle 11g闪回flashback
oracle9i的闪回：
闪回查询从9i引入，可以按照时间点或者SCN向前查
询，获取修改 前的数据。
闪回查询依赖于回滚段中存储的数据前镜像，通过设置
undo_retention参数设置前镜像的保留时间。
查询的语法：
select … as of scn | timestamp
Connected to Oracle Database 11g Enterprise Edition Release 11.2.0.1.0
Connected as hr@JIAGULUN
SQL> select * from student;
ID NAME AGE
----------- -------------------- -----------
1 zhangsan 21
2 lisi 22
3 wangwu 23
SQL> select to_char(sysdate,'yyyymmdd hh24:mi:ss') from dual;
TO_CHAR(SYSDATE,'YYYYMMDDHH24:
------------------------------
20150124 17:58:58
SQL>
SQL> update student s set s.name='mazi' where s.id = 1;
1 row updated
SQL> select to_char(sysdate,'yyyymmdd hh24:mi:ss') from dual;
TO_CHAR(SYSDATE,'YYYYMMDDHH24:
------------------------------
20150124 18:02:56
SQL> delete from student s where s.name = 'lisi';
1 row deleted
SQL> select * from student;
ID NAME AGE
----------- -------------------- -----------
1 mazi 21
3 wangwu 23
SQL> select to_char(sysdate,'yyyymmdd hh24:mi:ss') from dual;
TO_CHAR(SYSDATE,'YYYYMMDDHH24:
------------------------------
20150124 18:04:00
SQL> delete from student;
2 rows deleted
SQL> select * from student;
ID NAME AGE
----------- -------------------- -----------
SQL> select to_char(sysdate,'yyyymmdd hh24:mi:ss') from dual;
TO_CHAR(SYSDATE,'YYYYMMDDHH24:
------------------------------
20150124 18:04:26
SQL> select * from student as of scn 3099731;
ID NAME AGE
----------- -------------------- -----------
1 zhangsan 21
2 lisi 22
3 wangwu 23
SQL> select * from student;
ID NAME AGE
----------- -------------------- -----------
SQL> commit;
Commit complete
SQL> insert into student values(1,'zhangsan',23);
1 row inserted
SQL> commit;
Commit complete
SQL>
SQL> select to_char(sysdate,'yyyymmdd hh24:mi:ss') from dual;
TO_CHAR(SYSDATE,'YYYYMMDDHH24:
------------------------------
20150124 19:36:30
SQL>
SQL> delete from student;
1 row deleted
SQL> commit;
Commit complete
SQL> select to_char(sysdate,'yyyymmdd hh24:mi:ss') from dual;
TO_CHAR(SYSDATE,'YYYYMMDDHH24:
------------------------------
20150124 19:36:51
SQL> select * from student as of timestamp to_date('20150124 19:36:30','yyyymmdd hh24:mi:ss');
ID NAME AGE
----------- -------------------- -----------
1 zhangsan 23
SQL> select * from student as of timestamp to_date('20150124 18:04:26','yyyymmdd hh24:mi:ss');
ID NAME AGE
----------- -------------------- -----------
1 zhangsan 21
2 lisi 22
3 wangwu 23
SQL>
oracle10g的闪回版本查询：
对于9i的闪回查询进行增强，Oracle10g提供了闪回版本
查询，因为9i的闪回查询仅仅能够得到过去某个时间点上的
数据，但是无法反映出一段时间内数据表中数据的变化，
10g的闪回版本查询可以对时间段内数据表的不同版本进行
查询。
闪回版本查询的语法：
select … from … versions between
其中，select后面可以选择伪列，来获得事务的开始、结
束时间、SCN号、ID号等。
SQL> select to_char(sysdate,'yyyymmdd hh24:mi:ss') from dual;
TO_CHAR(SYSDATE,'YYYYMMDDHH24:
------------------------------
20150124 19:40:11
