1       创建表

SQL>create table wdongh(

  2  id  integer,

  3  name  varchar2(60)

  4  );

2       插入数据

SQL>insert into wdongh values(1,'wdh');

1 rowinserted

SQL>insert into wdongh values(2,'xiaoming');

1 rowinserted

SQL>insert into wdongh values(3,'hanmei');

1 rowinserted

SQL>insert into wdongh values(4,'leilei');

1 rowinserted

SQL>select * from wdongh;

                     ID               NAME

-----------      -----------

                      1               wdh

                      2               xiaoming

                      3               hanmei

                      4               leilei

3       删除数据

SQL>delete from wdongh;

4 rowsdeleted

SQL>commit;

Commitcomplete

SQL>select * from wdongh;

                    ID               NAME

-----------      -----------

4       获得当前SCN

Oracle 仅根据 SCN 执行恢复，它定义了数据库在某个确切时刻提交的版本。在事务提交时，它被赋予一个唯一的标示事物的SCN 。获得当前SCN的目的是：可以进行闪回查询尝试.

SQL>select dbms_flashback.get_system_change_number from dual;

GET_SYSTEM_CHANGE_NUMBER

------------------------

                  668754

SQL>select count(*) from wdongh as of scn 668754;

  COUNT(*)

----------

         0

5       确定delete时的scn号 5.1   建立一个临时表用于存储在scn为多少的时候执行了delete

SQL>create table temp(count int,scn int);

Tablecreated

5.2   往临时表中加入数据

SQL>declare

  2  iint :=668700;

  3 begin

  4  fori in 668700..668754 loop

  5   insert into temp (scn) values (i);

  6   update  temp set count=(selectcount(*) from wdongh as of scn i) where scn=i;

  7  endloop;

  8  end;

  9  /

PL/SQLprocedure successfully completed

SQL>commit;

Commitcomplete

5.3   查询scn为多少时执行了delete

SQL>select  * from temp where count >0;

                                  COUNT                                     SCN

------------                   -------------

                                      4                                  668700

                                      4                                  668701

                                      4                                  668702

                                      4                                  668703

                                      4                                  668704

                                      4                                  668705

                                      4                                  668706

                                      4                                  668707

8 rowsselected

SQL>select count(*) from wdongh as of scn 668707;

  COUNT(*)

----------

         4

SQL>select count(*) from wdongh as of scn 668708;

  COUNT(*)

----------

         0

我们看到在scn为668707时数据还在，即scn为668708就是我们delete的事务号。

6       恢复数据

SQL>insert into wdongh select * from wdongh as of scn 668707;

4 rowsinserted

SQL>select count(*) from wdongh;

  COUNT(*)

----------

         4

7       干掉临时表temp

SQL>drop table temp;

Tabledropped

SQL>commit;

Commitcomplete