Oracle 基于事务的临时表在11g和12C下，可以看到收集临时表的统计信息后，前者记录被清空，后者没有，这是个很重要的区别。在公司环境上用的是12C，在现场用的是11g，使用临时表会造成时快时慢，之前我有帖子，用了hint之后，也不是特别好，于是直接采集，结果临时表被清空。解决的方法是：建基于session的临时表，且每次用完之后要truncate，要不然，会有问题。
SQL> select * from v$version;
BANNER CON_ID
-------------------------------------------------------------------------------- ----------
Oracle Database 12c Enterprise Edition Release 12.1.0.1.0 - 64bit Production 0
PL/SQL Release 12.1.0.1.0 - Production 0
CORE 12.1.0.1.0Production 0
TNS for Linux: Version 12.1.0.1.0 - Production 0
NLSRTL Version 12.1.0.1.0 - Production 0
SQL> drop table test purge;
--基于事务的临时表
SQL> create global temporary table test
(
ID number
)
on commit delete rows;
SQL> insert into test select object_id from dba_objects;
99412 rows inserted
SQL> select count(1) from test;
COUNT(1)
----------
99412
SQL> exec dbms_stats.gather_table_stats(user,'test');
SQL> select count(1) from test;
COUNT(1)
----------
99412
SQL> select * from v$version;
BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
PL/SQL Release 11.2.0.1.0 - Production
CORE 11.2.0.1.0Production
TNS for Linux: Version 11.2.0.1.0 - Production
NLSRTL Version 11.2.0.1.0 - Production
SQL> drop table test purge;
--基于事务的临时表
SQL> create global temporary table test
(
ID number
)
on commit delete rows;
SQL> insert into test select object_id from dba_objects;
70379 rows inserted
SQL> select count(1) from test;
COUNT(1)
----------
70379
SQL> exec dbms_stats.gather_table_stats(user,'test');
SQL> select count(1) from test;
COUNT(1)
----------
0
在CentOS 6.4下安装Oracle 11gR2(x64)