语法： drop table ... purge;
例子：drop table test purge;
purge是直接删除表，不保留到回收站，10G开始默认drop表式改名移动到回收站;
闪回（flashback）语句：
1、能在一个语句中把表恢复到指定的时间点；
2、恢复表数据连同索引与约束信息；
3、能返回表及其内容到指定时间点或系统变更号（SCN）；
4、修复表的误操作
闪回简单示例：
SQL> drop table emp2;
Table dropped
SQL> select original_name,operation,droptime from recyclebin;
ORIGINAL_NAME OPERATION DROPTIME
-------------------------------- --------- -------------------
EMP2 DROP 2012-11-16:10:49:13
SQL> flashback table emp2 to before drop;
Done
SQL> select count(*) from emp2;
COUNT(*)
----------
107
--恢复误删表数据示例：
SQL> select sysdate 时间, timestamp_to_scn(sysdate) SCN from dual;
时间 SCN
----------- ----------
2012/11/16 1230043
SQL> delete from emp2;
107 rows deleted
SQL> commit;
Commit complete
SQL> select count(*) from emp2;
COUNT(*)
----------
0
SQL> flashback table emp2 to scn 1230043;
flashback table emp2 to scn 1230043
ORA-08189: cannot flashback the table because row movement is not enabled
SQL> alter table emp2 enable row movement;
Table altered
SQL> flashback table emp2 to scn 1230043;
Done
SQL> select count(*) from emp2;
COUNT(*)
----------
107