You verified that no table named SALES_TAB exists in the schema. Then you executed the following command to purge the objects in the recycle bin:
SQL> PURGE TABLE sales_tab;
What would be the outcome of this command?
A. All three tables in the recycle bin are purged
B. Only the table with the oldest DROPSCN is purged
C. The command returns an error because multiple entries with the same name exist in the recycle bin
D. Only the table with the latest DROPSCN is purged
Answer: B
每次清除一个在回收站中的对象，清除的是最早在回收站中的对象。
参考：http://docs.oracle.com/cd/E11882_01/server.112/e41084/statements_9018.htm#SQLRF55167
SQL> conn hr/hr
已连接。
SQL> create table cow977 ( id number(7));
表已创建。
SQL> insert into cow977 values (1234);
已创建 1 行。
SQL> drop table cow977;
表已删除。
SQL> create table cow977 ( a varchar2(10));
表已创建。
SQL> insert into cow977 values ('1234');
已创建 1 行。
SQL> drop table cow977;
表已删除。
SQL> select OBJECT_NAME,ORIGINAL_NAME, CREATETIME, DROPTIME from user_recyclebin;
OBJECT_NAME ORIGINAL_NAME CREATETIME DROPTIME
------------------------------ -------------------------------- ------------------- -------------------
BIN$h/MVcV9OTdaAPbSxNTVioA==$0 COW977 2016-06-16:19:55:00 2016-06-16:19:55:32
BIN$a/IbfeulSIutf/fwwwNp4A==$0 COW977 2016-06-07:11:13:30 2016-06-07:11:18:05
BIN$6UANFu87S16yiJj+eRZsMA==$0 COW977 2016-06-16:19:55:54 2016-06-16:19:56:11
SQL> purge table cow977;
表已清除。
SQL> select OBJECT_NAME,ORIGINAL_NAME, CREATETIME, DROPTIME from user_recyclebin;
OBJECT_NAME ORIGINAL_NAME CREATETIME DROPTIME
------------------------------ -------------------------------- ------------------- -------------------
BIN$h/MVcV9OTdaAPbSxNTVioA==$0 COW977 2016-06-16:19:55:00 2016-06-16:19:55:32
BIN$6UANFu87S16yiJj+eRZsMA==$0 COW977 2016-06-16:19:55:54 2016-06-16:19:56:11
SQL> purge table cow977;
表已清除。
SQL> select OBJECT_NAME,ORIGINAL_NAME, CREATETIME, DROPTIME from user_recyclebin;
OBJECT_NAME ORIGINAL_NAME CREATETIME DROPTIME
------------------------------ -------------------------------- ------------------- -------------------
BIN$6UANFu87S16yiJj+eRZsMA==$0 COW977 2016-06-16:19:55:54 2016-06-16:19:56:11
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