http://huakaibird.itpub.net 搞懂oracle字符集作为一个ORACLE DBA,在工作中会经常处理由于字符集产生的一些问题。但是当真正想写一些这方面的东西时，却突然又没有了头绪。发了半天呆，还是决定用两个字符集方面的例子作为切入点，倒不失为一个头绪，说不定在实验的过程中，问题就会一个接着一个的浮现出来。现在，让我们切入正题。我用的数据库是oracle10.2.0.3,数据库字符集是al32utf8。客户端就是同一台机器的windows xp.下面是演示的例子：SQL> drop table test purge;Table dropped.SQL> create table test(col1 number(1),col2 varchar2(10));Table created.--s... http://huakaibird.itpub.net/post/19599/490972 Wed,02 09 2009 10:42:25 export: mysqldump database [table] > /tmp/filenameimport: mysql database < /tmp/filenamecan add "max_allowed_packet=104857600" under [mysqld] in /etc/my.cnf file to resolve the "Got a packet bigger than 'max_allowed_packet' bytes" problem.There is some problems with this import method.If the mysqldump version is low, the triggers and procedure can not be export. You can upgrade the mysqldump or use remote new version mysqldump to export.trigger is default, procedure need parametermysqldump -u -p... http://huakaibird.itpub.net/post/19599/487484 Mon,13 07 2009 14:03:00 When there is no name-resolve, the mysql connection will be slow.Add 'skip-name-resolve' under '[mysqld]' section in /etc/my.cnf will resolve this problem. http://huakaibird.itpub.net/post/19599/487473 Mon,13 07 2009 11:14:30 Oracle escape string only valid to "_", "%" and itself.For example, use "" as escape string,like 'abc%' escape '', will encounter oracle ORA-01424 errorSo when support the escape string, must take care.Should Transfer the single '' with other string. http://huakaibird.itpub.net/post/19599/481988 Thu,09 04 2009 16:46:27 When using not in, not like, <>, not between in sql, you should pay attention, if the field is permit to null, the null value record can not be selected, you should add not null to let the null record shown. But the not exists is the except, it can select the null record, because the sql is always not exists(select field1 from table1 where table1.field1=table2.field1), if it table2's field1 is null, of course the equation is not true. http://huakaibird.itpub.net/post/19599/466134 Wed,09 07 2008 15:05:43 The recyclebin is just a virtual storage area, a data dictionary. When drop table, the real space on the tablespace this table take up would not deleted in deed. But if the space is not enough, Oracle will delete the space auto. http://huakaibird.itpub.net/post/19599/458929 Thu,03 04 2008 14:56:36 truncate 能释放表空间以及索引空间，但是前一次扩展的索引空间并不一定能记录到数据字典中， 故最好rebuild index. http://huakaibird.itpub.net/post/19599/457853 Fri,21 03 2008 17:03:39 free space 大于db file的大小遇到一个奇怪的问题， db file free space的大小大于file的大小。导致在toad下看到的使用率为负的select sum(bytes) from dba_free_space where file_id=8;result: 35672489984 (这个大小已经达到了数据文件的max)select bytes from dba_data_files where file_id=8;result: 10171187200由于oracle bug 5083393 导致， solution:purge tablespace TS_NAME;exec dbms_space_admin.tablespace_rebuild_bitmaps('TS_NAME'); http://huakaibird.itpub.net/post/19599/457852 Fri,21 03 2008 16:56:44 When you use form in html, you can have two value "post" or "get" for method get: With the HTTP "get" method, the form data set is appended to the URI specified by the action attribute (with a question-mark ("?") as separator) and this new URI is sent to the processing agent. post: With the HTTP "post" method, the form data set is included in the body of the form and sent to the processing agent. If use get, your action is "test.html?test=1", the "test=1" will be replaced by form data set, but i... http://huakaibird.itpub.net/post/19599/454520 Sun,03 02 2008 13:14:50 move oracle from '/opt' to '/disk'>shutdowncp all files;update environment.update pfile,change control files, background_dump_dest, core_dump_dest, user_dump_destsqlplus "/as sysdba"> startup mount pfile='new'>alter database rename file 'old' to 'new'>alter database openok http://huakaibird.itpub.net/post/19599/449394 Fri,04 01 2008 15:30:51