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Oracle 字符集
1.字符集查看方式;
2.服务端、客户端字符集设置;
3.乱码分析;
1.字符集查看方式:
1.1 通过 nls_database_parameters 视图查询数据库字符集(数据来源于props$):
1 SQL> select parameter,value from nls_database_parameters where parameter like ‘%CHARACTER%‘; 2 3 PARAMETER VALUE 4 ------------------------------ ------------------------------ 5 NLS_NUMERIC_CHARACTERS ., 6 NLS_CHARACTERSET AL32UTF8 7 NLS_NCHAR_CHARACTERSET AL16UTF16 8 Elapsed: 00:00:00.02
1.2 通过 nls_session_parameters 查询当前session 环境变量(数据来源于:X$NLS_PARAMETERS):
SQL> select * from nls_session_parameters;
1.3 通过v$nls_parameters 视图查询(数据来源于:X$NLS_PARAMETERS):
1 SQL> select parameter,value from v$nls_parameters where parameter like ‘%CHARACTER%‘; 2 3 PARAMETER VALUE 4 ---------------------------------------------------------------- ------------------------------ 5 NLS_NUMERIC_CHARACTERS ., 6 NLS_CHARACTERSET AL32UTF8 7 NLS_NCHAR_CHARACTERSET AL16UTF16 8 Elapsed: 00:00:00.01
1.4 通过用户环境变量查询:
1 SQL> select userenv(‘language‘) from dual; 2 3 USERENV(‘LANGUAGE‘) 4 ---------------------------------------------------- 5 AMERICAN_AMERICA.AL32UTF8 6 Elapsed: 00:00:00.03
获得的结果包括:语言(NLS_LANGUAGE)、地区(NLS_TERRITORY)、字符集(NSL_CHARACTERSET);
2.服务端、客户端字符集设置:
2.1 服务端字符集设置:
数据库创建时提供字符集设置,通常是操作系统平台字符集,也可以在创建数据库后修改字符集,但新的字符集必须支持旧的字符集(旧字符集的超集);
修改前备份所有数据,修改字符集后导入数据到新字符集中;
修改步骤:
1 SQL> shutdown immediate 2 SQL> startup nomount 3 SQL> alter database mount exclusive; --装载数据为专用的高级模式; 4 SQL> alter system enable restricted session; --启用受限制的session模式 5 SQL> alter system set job_queue_processes=0; --‘maximum number of job queue slave processes‘ 设置工作队列的最大进程数为0 6 SQL> alter system set aq_tm_processes=0; 7 SQL> alter database open; 8 SQL> alter database character set AL32UTF8; --新的字符集必须支持旧的字符集(旧字符集的超集),相关错误:(ORA-12712: new character set must be a superset of old character set) 9 SQL> shutdown immediate 10 SQL> startup
重启后字符集改变:
1 Verifying file header compatibility for 11g tablespace encryption.. 2 Verifying 11g file header compatibility for tablespace encryption completed 3 SMON: enabling tx recovery 4 Database Characterset is AL32UTF8 5 No Resource Manager plan active 6 replication_dependency_tracking turned off (no async multimaster replication found) 7 WARNING: AQ_TM_PROCESSES is set to 0. System operation might be adversely affected. 8 Completed: ALTER DATABASE OPEN
2.2 客户端字符集设置:
当客户端连接服务端时读取环境变量NLS_LANG和其它环境变量,当设置了NLS_LANG 环境变量后,想关环境变量(NLS_LANGUAGE、NLS_TERRITORY)会因该变量的设置而变化,因为它们默认情况下都是源于NLS_LANG环境变量;其它的环境变量(NLS_DATE_FORMAT、NLS_TIMESTAMP_FORMAT、NLS_NUMBERIC_CHARACTERS..)会因NLS_TERRITORY变量的设置而变化;WINDOWS 平台上NLS_LANG环境变量被设置在注册表内,在我的机器中默认值是:SIMPLIFIED CHINESE_CHINA.ZHS16GBK,LINUX 平台上通过NLS_LANG设置,如未设置或安装时使用Oracle Universal Install 安装,NLS_LANG环境变量是不会被设置的,其默认值为:AMERICAN_AMERICA.US7ASCII;
3.乱码分析:
以当前的环境为例,我并未设置NLS_LANG 环境变量,数据库的字符码为:AMERICAN_AMERICA.AL32UTF8
1 SQL> select userenv(‘language‘) from dual; 2 3 USERENV(‘LANGUAGE‘) 4 ---------------------------------------------------- 5 AMERICAN_AMERICA.AL32UTF8
而操作系统的字符集是:
1 [sywu@wusuyuan ~]$ locale 2 LANG=zh_CN.UTF-8
查询数据和插入数据都是乱码的:
1 SQL> select * from tb_distree; 2 3 ID NAME 4 ---------- ------------------------------------------------------------------ 5 3 ?? 6 3 ?? 7 4 ?? 8 5 ?? 9 SQL> insert into tb_distree values(17,‘德国‘); 10 11 1 row created.
从10046 trace 中已经可以清晰看出后台乱码
1 SQL ID: 5naprsgt1dqj3 2 108 Plan Hash: 0 3 109 insert into tb_distree 4 110 values 5 111 (18,‘??????‘) 6 112 7 113 8 114 call count cpu elapsed disk query current rows 9 115 ------- ------ -------- ---------- ---------- ---------- ---------- ---------- 10 116 Parse 1 0.00 0.00 0 0 0 0 11 117 Execute 1 0.02 0.02 0 1 5 1 12 118 Fetch 0 0.00 0.00 0 0 0 0 13 119 ------- ------ -------- ---------- ---------- ---------- ---------- ---------- 14 120 total 2 0.02 0.02 0 1 5 1 15 121 16 122 Misses in library cache during parse: 1 17 123 Optimizer mode: ALL_ROWS 18 124 Parsing user id: 85 19 125 20 126 Rows Row Source Operation 21 127 ------- --------------------------------------------------- 22 128 0 LOAD TABLE CONVENTIONAL (cr=1 pr=0 pw=0 time=0 us) 23 129
但此时数据库的字符集是AMERICAN_AMERICA.AL32UTF8,只是没有设置NLS_LANG环境变量且机器本身的字符集与数据库字符集不一致,在官方文档中表明该环境变量在未设置时默认为:AMERICAN_AMERICA.US7ASCII,US7ASCII字符集本身不支持中文,保存数据时,数据库进行字符转换,从US7ASCII转换为AL32UTF8;
1 SQL> select id,name,dump(name,‘1016‘) from tb_distree; 2 3 ID NAME DUMP(NAME,‘1016‘) 4 ---------- ---------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- 5 3 ?? Typ=1 Len=6 CharacterSet=AL32UTF8: e4,ba,91,e5,8d,97 6 3 ?? Typ=1 Len=6 CharacterSet=AL32UTF8: e5,b9,bf,e4,b8,9c 7 4 ?? Typ=1 Len=6 CharacterSet=AL32UTF8: e5,8c,97,e4,ba,ac 8 5 ?? Typ=1 Len=6 CharacterSet=AL32UTF8: e5,9b,9b,e5,b7,9d 9 18 ?????? Typ=1 Len=18 CharacterSet=AL32UTF8: ef,bf,bd,ef,bf,bd,ef,bf,bd,ef,bf,bd,ef,bf,bd,ef,bf,bd
经尝试怎么转换都是乱码:
1 SQL> select convert(‘中国‘,‘US7ASCII‘) from dual; 2 3 CO 4 -- 5 ?? 6 7 SQL> select convert(convert(‘中国‘,‘US7ASCII‘),‘AL32UTF8‘) FROM DUAL; 8 9 CO 10 -- 11 ??
设置环境变量:
1 [sywu@wusuyuan ~]$ export NLS_LANG=AMERICAN_AMERICA.AL32UTF8 2 [sywu@wusuyuan ~]$ echo $NLS_LANG 3 AMERICAN_AMERICA.AL32UTF8 4 5 SQL> select * from tb_distree; 6 7 ID NAME 8 ---------- ---------- 9 3 云南 10 3 广东 11 4 北京 12 5 四川 13 6 重庆 14 7 上海 15 8 香港 16 15 ?????? 17 17 ?????? 18 18 ??????
这样字符就显示正常了,但之前在没有设置环境变量NLS_LANG=AMERICAN_AMERICA.AL32UTF8之前插入的数据依旧是乱码;总结:当客户端和服务端字符集相同时,不存在字符集转换,数据直接保存数据;当客户端和服务端字符集不相同时,在设置了NLS_LANG环境变量(未设置默认值:AMERICAN_AMERICA.US7ASCII)时,保存或提前数据,数据库都要经过字符转换,正确一致的设置字符集可以提高数据库效率;