转载请注明出处：
正确答案：ACE
建临表有两种类型：
分别创建如下：
(1)当提交时，将自动清除表中所有数据。
gyj@OCM> create global temporary table temp_t1(id int,name varchar2(10)) on commit delete rows; gyj@OCM> insert into temp_t1 values(1,'AAAAA'); 1 row created. gyj@OCM> select * from temp_t1; ID NAME ---------- ---------- 1 AAAAA
提交后再查temp_t1，没有记录了。
gyj@OCM> commit; Commit complete. gyj@OCM> select * from temp_t1; no rows selected
(2)只有当会话退出后，临时表中的行才会被清除。
gyj@OCM> create global temporary table temp_t2(id int,name varchar2(10)) on commit preserve rows; Table created. gyj@OCM> insert into temp_t2 values(1,'AAAAA'); 1 row created. gyj@OCM> commit; Commit complete. gyj@OCM> select * from temp_t2; ID NAME ---------- ---------- 1 AAAAA开另一会话，查temp_t2，结果如下：
gyj@OCM> select sid from v$mystat where rownum=1; SID ---------- 16 gyj@OCM> select * from temp_t2; no rows selected
说明临时表是私有的，每个会话只能查到当前会话下自己DML的数据，每个会话互不干涉，因此临时表不需要锁。
我们来解析答案：
答案A,正确，在临时表上可以创建索引和视图，实验如下：
（1）创建索引
gyj@OCM> create index indx_temp_t2 on temp_t1(id);
Index created.
（2）创建视图
gyj@OCM> create view v_temp_t2 as select * from temp_t2;
View created.
答案B：不正确，只能导出临时表结构而不能导出临时表中的数据。
[oracle@mydb ~]$ exp gyj/gyj file=/home/oracle/gyj.dmp; Export: Release 11.2.0.3.0 - Production on Tue Sep 24 21:04:44 2013 Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved. Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production With the Partitioning, OLAP, Data Mining and Real Application Testing options Export done in ZHS16GBK character set and AL16UTF16 NCHAR character set About to export specified users ... . exporting pre-schema procedural objects and actions . exporting foreign function library names for user GYJ . exporting PUBLIC type synonyms . exporting private type synonyms . exporting object type definitions for user GYJ About to export GYJ's objects ... . exporting database links . exporting sequence numbers . exporting cluster definitions . about to export GYJ's tables via Conventional Path ... . . exporting table DEPT 2 rows exported . . exporting table EMP 3 rows exported . . exporting table NEW_ORDER 1 rows exported . . exporting table T1 2 rows exported . . exporting table T100 2 rows exported . . exporting table TEMP_T1 . . exporting table TEMP_T2 . exporting synonyms . exporting views . exporting stored procedures . exporting operators . exporting referential integrity constraints . exporting triggers . exporting indextypes . exporting bitmap, functional and extensible indexes . exporting posttables actions . exporting materialized views . exporting snapshot logs . exporting job queues . exporting refresh groups and children . exporting dimensions . exporting post-schema procedural objects and actions . exporting statistics Export terminated successfully without warnings.
如果不信你可以把gyj.dmp数据用工具imp导入另一个用户,然后查一下temp_t1,temp_t2临时表中有没有数据，这个我就不做了，留给大家思考、实践。临时表是私有的数据只是临时存放，提交或着退出会话都会释放临时表中的数据。
答案C，正确。临时表并非存放在用户的表空间中，而是存放在 Schema 所指定的临时表空间中。
gyj@OCM> Select Table_Name, Tablespace_Name From User_Tables Where Table_Name Like 'TEMP%'; TABLE_NAME TABLESPACE_NAME ------------------------------ ------------------------------ TEMP_T1 TEMP_T2
可见这两张临时表并未存放在用户的表空间中。
用户 GYJ的临时表空间是 TEMP , 用户创建的临时表是存放在TEMP表空间中的。下面来证明
gyj@OCM> SELECT UserName, Default_Tablespace def_ts, Temporary_Tablespace temp_ts FROM User_Users; USERNAME DEF_TS TEMP_TS ------------------------------ ------------------------------ ------------------------------ GYJ GYJ TEMP gyj@OCM> alter tablespace temp tempfile offline; alter tablespace temp tempfile offline * ERROR at line 1: ORA-12905: default temporary tablespace cannot be brought OFFLINE gyj@OCM> create temporary tablespace temp1 tempfile '/u01/app/oracle/oradata/ocm/temp02.dbf' size 10M; Tablespace created. gyj@OCM> alter database default temporary tablespace temp1; Database altered. gyj@OCM> alter tablespace temp tempfile offline; Tablespace altered. gyj@OCM> INSERT INTO TEMP_T2 VALUES(1,'AAAAA'); INSERT INTO TEMP_T2 VALUES(1,'AAAAA') * ERROR at line 1: ORA-00376: file 201 cannot be read at this time ORA-01110: data file 201: '/u01/app/oracle/oradata/ocm/temp01.dbf'
答案：D不正确。临时表是私有，不同的会话相互之间是不能看到对方操作的数据。以上有证明我就不再举例了。
答案：E正确。临时表是私有的，每个会话只能查到当前会话下自己DML的数据，每个会话互不干涉，因此临时表不需要锁。这个大家可以去实验验证。
QQ：252803295
技术交流QQ群：
DSI&Core Search Ⅰ 群：127149411（2000人技术群:未满）DSI&Core Search Ⅱ 群：177089463（1000人技术群:未满）DSI&Core Search Ⅲ 群：284596437（500人技术群:未满）DSI&Core Search Ⅳ 群：192136702（500人技术群:未满）DSI&Core Search Ⅴ 群：285030382（500人闲聊群:未满）MAIL：dbathink@hotmail.com
BLOG： http://blog.csdn.net/guoyjoe
WEIBO：http://weibo.com/guoyJoe0218
ITPUB： http://www.itpub.net/space-uid-28460966.html
OCM： http://education.oracle.com/education/otn/YGuo.HTM