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Oracle字符集问题小集

分类： Oracle

2008-07-15 17:01:55

影响oracle数据库字符集最重要的参数是NLS_LANG参数。它的格式如下:

　　NLS_LANG = language_territory.charset

　　它有三个组成部分(语言、地域和字符集)，每个成分控制了NLS子集的特性。其中:

　　Language 指定服务器消息的语言，territory 指定服务器的日期和数字格式，charset 指定字符集。如:AMERICAN _ AMERICA. ZHS16GBK

　　从NLS_LANG的组成我们可以看出，真正影响数据库字符集的其实是第三部分。所以两个数据库之间的字符集只要第三部分一样就可以相互导入导出数据，前面影响的只是提示信息是中文还是英文。

－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－

如何查询Oracle的字符集

　　很多人都碰到过因为字符集不同而使数据导入失败的情况。这涉及三方面的字符集，一是oracel server端的字符集，二是oracle client端的字符集;三是dmp文件的字符集。在做数据导入的时候，需要这三个字符集都一致才能正确导入。

 

1、查询oracle server端的字符集

　　有很多种方法可以查出oracle server端的字符集，比较直观的查询方法是以下这种:SQL>select userenv(‘language’) from dual;

　　结果类似如下:AMERICAN _ AMERICA. ZHS16GBK

2、如何查询dmp文件的字符集

　　用oracle的exp工具导出的dmp文件也包含了字符集信息，dmp文件的第2和第3个字节记录了dmp文件的字符集。如果dmp文件不大，比如只有几M或几十M，可以用UltraEdit打开(16进制方式)，看第2第3个字节的内容，如0354，然后用以下SQL查出它对应的字符集:

　　SQL> select nls_charset_name(to_number('0354','xxxx')) from dual;

　　ZHS16GBK

　　如果dmp文件很大，比如有2G以上(这也是最常见的情况)，用文本编辑器打开很慢或者完全打不开，可以用以下命令(在unix主机上):

　　cat exp.dmp |od -x|head -1|awk '{print $2 $3}'|cut -c 3-6

　　然后用上述SQL也可以得到它对应的字符集。

3、查询oracle client端的字符集

　　这个比较简单。在windows平台下，就是注册表里面相应OracleHome的NLS_LANG。还可以在dos窗口里面自己设置，比如:

　　set nls_lang=AMERICAN_AMERICA.ZHS16GBK

　　这样就只影响这个窗口里面的环境变量。

　　在unix平台下，就是环境变量NLS_LANG。

　　$echo $NLS_LANG

　　AMERICAN_AMERICA.ZHS16GBK

　　如果检查的结果发现server端与client端字符集不一致，请统一修改为同server端相同的字符集。

－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－

三、修改oracle的字符集

　　上文说过，oracle的字符集有互相的包容关系。如us7ascii就是zhs16gbk的子集,从us7ascii到zhs16gbk不会有数据解释上的问题,不会有数据丢失。在所有的字符集中utf8应该是最大,因为它基于unicode,双字节保存字符(也因此在存储空间上占用更多)。

　　一旦数据库创建后，数据库的字符集理论上讲是不能改变的。因此，在和安装之初考虑使用哪一种字符集十分重要。根据Oracle的官方说明，字符集的转换是从子集到超集受支持,反之不行。如果两种字符集之间根本没有子集和超集的关系，那么字符集的转换是不受oracle支持的。对数据库server而言，错误的修改字符集将会导致很多不可测的后果，可能会严重影响数据库的正常运行，所以在修改之前一定要确认两种字符集是否存在子集和超集的关系。一般来说，除非万不得已，我们不建议修改oracle数据库server端的字符集。特别说明，我们最常用的两种字符集ZHS16GBK和ZHS16CGB231280之间不存在子集和超集关系，因此理论上讲这两种字符集之间的相互转换不受支持。

　　1、修改server端字符集(不建议使用)

　　在oracle 8之前，可以用直接修改数据字典表props$来改变数据库的字符集。但oracle8之后，至少有三张系统表记录了数据库字符集的信息，只改props$表并不完全，可能引起严重的后果。正确的修改方法如下:

　　$sqlplus /nolog

　　SQL>conn / as sysdba;

　　若此时数据库服务器已启动，则先执行SHUTDOWN IMMEDIATE命令关闭数据库服务器，然后执行以下命令:

　　SQL>STARTUP MOUNT;

　　SQL>ALTER SYSTEM ENABLE RESTRICTED SESSION;

　　SQL>ALTER SYSTEM SET JOB_QUEUE_PROCESSES=0;

　　SQL>ALTER SYSTEM SET AQ_TM_PROCESSES=0;

　　SQL>ALTER DATABASE OPEN;

　　SQL>ALTER DATABASE CHARACTER SET ZHS16GBK;

　　SQL>ALTER DATABASE national CHARACTER SET ZHS16GBK;

　　SQL>SHUTDOWN IMMEDIATE;

　　SQL>STARTUP

　　2、修改dmp文件字符集

　　上文说过，dmp文件的第2第3字节记录了字符集信息，因此直接修改dmp文件的第2第3字节的内容就可以‘骗’过oracle的检查。这样做理论上也仅是从子集到超集可以修改，但很多情况下在没有子集和超集关系的情况下也可以修改，我们常用的一些字符集，如US7ASCII，WE8ISO8859P1，ZHS16CGB231280，ZHS16GBK基本都可以改。因为改的只是dmp文件，所以影响不大。

　　具体的修改方法比较多，最简单的就是直接用UltraEdit修改dmp文件的第2和第3个字节。比如想将dmp文件的字符集改为ZHS16GBK，可以用以下SQL查出该种字符集对应的16进制代码:

　　SQL> select to_char(nls_charset_id('ZHS16GBK'), 'xxxx') from dual;

　　0354

　　然后将dmp文件的2、3字节修改为0354即可。

　　如果dmp文件很大，用ue无法打开，就需要用程序的方法了。网上有人用java存储过程写了转换的程序(用java存储过程的好处是通用性教好，缺点是比较麻烦)。我在windows下测试通过。但要求oracle数据库一定要安装JVM选项。有兴趣的朋友可以研究一下程序代码－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－

 

Character Encoding Schemes

Single-Byte 7-Bit Encoding Schemes

Single-Byte 8-Bit Encoding Schemes

Multi-Byte Encoding Schemes

shift-out code indicates that the following bytes are double-byte characters until a shift-in code is encountered.

There are two general groups of encoding schemes, those based on 7-bit ASCII and those based on IBM EBCDIC. Within each group, all schemes normally use the same encoding for the 26 Latin characters (A to Z), but use different encoding for other characters used in languages other than English. ASCII and EBCDIC use different encodings, even for the Latin characters.

--------------------------

Specifying Language-Dependent Behavior

This section discusses the parameters that specify language-dependent operation. You can set language-dependent behavior defaults for the server and set language dependent behavior for the client that overrides these defaults.

  • As initialization parameters to specify language-dependent behavior defaults for the server.
    For example, in your INIT.ORA file, include
		NLS_TERRITORY = FRANCE

  • As environment variables on client machines to specify language-dependant behavior defaults for a session. These defaults override the defaults set for the server.
    For example, on a UNIX system
		setenv NLS_TERRITORY FRANCE

  • As ALTER
    For example:
		ALTER SESSION SET NLS_TERRITORY = FRANCE
 
 

NLS Parameters

The NLS_LANGUAGE and NLS_TERRITORY parameters implicitly specify several aspects of language-dependent operation. Additional NLS parameters provide explicit control over these operations. The parameters listed below can be specified in the initialization file, or they can also be specified for each session with the ALTER SESSION command.

Parameter Description
NLS_CALENDAR Calendar system
NLS_CURRENCY Local currency symbol
NLS_DATE_FORMAT Default date format
NLS_DATE_LANGUAGE Default language for dates
NLS_ISO_CURRENCY ISO international currency symbol
NLS_LANGUAGE Default language
NLS_NUMERIC_CHARACTERS Decimal character and group separator
NLS_SORT Character sort sequence
NLS_SPECIAL_CHARS
NLS_TERRITORY Default territory
For a complete description of ALTER SESSION, see .

NLS_CALENDAR

Many different calendar systems are in use throughout the world. NLS_CALENDAR specifies which calendar system Oracle uses.

NLS_CALENDAR can have one of the following values:

  • Arabic Hijrah
  • Gregorian
  • Japanese Imperial
  • Persian
  • ROC Official
  • Thai Buddha

For example, if NLS_CALENDAR is set to "Japanese Imperial", the date format is "YY-MM-DD", and the date is February 17, 1907, then the sysdate is displayed as follows: 

SELECT SYSDATE FROM DUAL;
SYSDATE
--------
07-02-17 
 
NLS_CURRENCY
This parameter specifies the character string returned by the number format mask L, the local currency symbol, overriding that defined implicitly by NLS_TERRITORY. For example, to set the local currency symbol to "Dfl" (including a space), the parameter should be set as follows: 
NLS_CURRENCY = "Dfl "
In this case, the query 
SELECT TO_CHAR(TOTAL, 'L099G999D99') "TOTAL"
   FROM ORDERS WHERE CUSTNO = 586
would return 
TOTAL
-------------
Dfl 12.673,49
You can alter the default value of NLS_CURRENCY by changing its value in the initialization file and then restarting the instance, and you can alter its value during a session using an ALTER SESSION SET NLS_CURRENCY command. 
For a complete description of ALTER SESSION, see . 
NLS_DATE_FORMAT
Defines the default date format to use with the TO_CHAR 
NLS_DATE_FORMAT = "MM/DD/YYYY"
As another example, to set the default date format to display Roman numerals for months, you would include the following line in your initialization file: 
 
SELECT TO_CHAR(SYSDATE) CURRDATE
   FROM DUAL;
CURRDATE
---------
13 II 91
The value of this parameter is stored in the tokenized internal date format. Each format element occupies two bytes, and each string occupies the number of bytes in the string plus a terminator byte. Also, the entire format mask has a two-byte terminator. For example, "MM/DD/YY" occupies 12 bytes internally because there are three format elements, two one-byte strings (the two slashes), and the two-byte terminator for the format mask. The tokenized format for the value of this parameter cannot exceed 24 bytes. 
Note: The applications you design may need to allow for a variable-length default date format. Also, the parameter value must be surrounded by double quotes: single quotes are interpreted as part of the format mask. 
You can alter the default value of NLS_DATE_FORMAT by changing its value in the initialization file and then restarting the instance, and you can alter the value during a session using an ALTER SESSION SET NLS_DATE_FORMAT command. 
For a complete description of ALTER SESSION, see . 
NLS_DATE_ LANGUAGE
This parameter specifies the language for the spelling of day and month names by the functions TO_CHAR 
NLS_DATE_LANGUAGE = FRENCH
In this case, the query 
SELECT TO_CHAR(SYSDATE, 'Day:Dd Month yyyy')
   FROM DUAL;
would return 
Mercredi:13 Février 1991
 
Me:13 Fév 1991
 
INSERT INTO tablename VALUES ('13-Fév-1991');
 
SELECT TO_CHAR(TO_DATE('27-Fév-91'),'Day: ddspth Month')
   FROM DUAL;
would return: 
Mercredi: twenty-seventh Février
You can alter the default value of NLS_DATE_LANGUAGE by changing its value in the initialization file and then restarting the instance, and you can alter the value during a session using an ALTER SESSION SET NLS_DATE_LANGUAGE command. 
For a complete description of ALTER SESSION, see . 
NLS_ISO_CURRENCY
This parameter specifies the character string returned by the number format mask C, the ISO currency symbol, overriding that defined implicitly by NLS_TERRITORY. 
Local currency symbols can be ambiguous; for example, a dollar sign ($) can refer to US dollars or Australian dollars. ISO Specification 4217 1987-07-15 defines unique "international" currency symbols for the currencies of specific territories (or countries). 
For example, the ISO currency symbol for the US Dollar is USD, for the Australian Dollar AUD. To specify the ISO currency symbol, the corresponding territory name is used. 
NLS_ISO_CURRENCY has the same syntax as the NLS_TERRITORY parameter, and all supported territories are valid values. For example, to specify the ISO currency symbol for France, the parameter should be set as follows: 
NLS_ISO_CURRENCY = FRANCE
In this case, the query 
SELECT TO_CHAR(TOTAL, 'C099G999D99') "TOTAL"
   FROM ORDERS WHERE CUSTNO = 586
would return 
TOTAL
-------------
 FRF12.673,49
For a complete description of ALTER SESSION, see . 
NLS_NUMERIC_ CHARACTERS
 
NLS_NUMERIC_CHARACTERS = ",."
Both characters are single byte and must be different. Either can be a space. 
Note: When the decimal character is not a period (.) or when a group separator is used, numbers appearing in SQL statements must be enclosed in quotes. For example: 
        INSERT INTO SIZES (ITEMID, WIDTH, QUANTITY)
          VALUES (618, '45,5', TO_NUMBER('1.234','9G999'));
You can alter the default value of NLS_NUMERIC_CHARACTERS by changing its value in the initialization file and then restarting the instance, and you can alter its value during a session using an ALTER SESSION SET NLS_DATE_LANGUAGE command. 
For a complete description of ALTER SESSION, see . 
NLS_SORT
The syntax of NLS_SORT is: 
NLS_SORT = { BINARY | name }
BINARY specifies a binary sort and name specifies a particular linguistic sort sequence. For example, to specify the linguistic sort sequence called German, the parameter should be set as follows: 
NLS_SORT = German
The name given to a linguistic sort sequence has no direct connection to language names. Usually, however, each supported language will have an appropriate linguistic sort sequence defined that uses the same name. 
Note: Setting the NLS_SORT initialization parameter to BINARY causes a sort to use a full table scan, regardless of the path the optimizer chooses. 
You can alter the default value of NLS_SORT by changing its value in the initialization file and then restarting the instance, and you can alter its value during a session using an ALTER SESSION SET NLS_SORT command. 
For a complete description of ALTER SESSION, see . 
A complete list of linguistic definitions is provided in the .
 
_______________________________________________________________________
NLS Data
This section lists supported languages, territories, storage character sets, Arabic/Hebrew display character sets, linguistic definitions, and calendars. 
Supported Languages
The following languages are supported in Oracle Server release 7.3: 
 
Supported Territories
The following territories are supported in Oracle Server release 7.3: 
 
 
 
Table C-2 Oracle Character Sets for Operating System Locales   
Operating System Locale
Character Set
Arabic
AR8ASMO8X
Catalan
WE8PC850
Chinese (PRC)
ZHS16GBK
Chinese (Taiwan)
ZHT16MSWIN950
Czech 
EE8PC852 
Danish 
WE8PC850 
Dutch 
WE8PC850 
English (United Kingdom)
WE8PC850
English (United States)
US8PC437
Finnish 
WE8PC850 
French
WE8PC850 
German
WE8PC850 
Greek
EL8PC737 
Hungarian
EE8PC852 
Italian
WE8PC850
Japanese
JA16SJIS
Korean
KO16MSWIN949
Norwegian
WE8PC850 
Polish
EE8PC852 
Portuguese 
WE8PC850
Romanian
EE8PC852 
Russian
RU8PC866 
Slovak 
EE8PC852 
Slovenian 
EE8PC852
Spanish
WE8PC850 
Swedish
WE8PC850 
Turkish
TR8PC857
 
Storage Character Sets
The following storage character sets are supported in Oracle Server release 7.3: 
Name Description 
US7ASCII ASCII 7-bit American 
WE8DEC DEC 8-bit West European 
WE8HP HP LaserJet 8-bit West European 
US8PC437 IBM-PC Code Page 437 8-bit American 
WE8EBCDIC37 EBCDIC Code Page 37 8-bit West European 
WE8EBCDIC500 EBCDIC Code Page 500 8-bit West European 
WE8PC850 IBM-PC Code Page 850 8-bit West European 
D7DEC DEC VT 100 7-bit German 
F7DEC DEC VT 100 7-bit French 
S7DEC DEC VT100 7-bit Swedish 
E7DEC DEC VT100 7-bit Spanish 
SF7ASCII ASCII 7-bit Finnish 
NDK7DEC DEC VT100 7-bit Norwegian/Danish 
I7DEC DEC VT100 7-bit Italian 
NL7DEC DEC VT100 7-bit Dutch 
CH7DEC DEC VT100 7-bit Swiss (German/French) 
YUG7ASCII ASCII 7-bit Yugoslavian 
SF7DEC DEC VT 100 7-bit Finnish 
TR7DEC DEC VT100 7-bit Turkish 
WE8ISO8859P1 ISO 8859-1 West European 
EE8ISO8859P2 ISO 8859-2 East European 
SE8ISO8859P3 ISO 8859-3 South European 
NEE8ISO8859P4 ISO 8859-4 North and North-East European 
CL8ISO8859P5 ISO 8859-5 Latin/Cyrillic 
AR8ISO8859P6 ISO 8859-6 Latin/Arabic 
EL8ISO8859P7 ISO 8859-7 Latin/Greek 
IW8ISO8859P8 ISO 8859-8 Latin/Hebrew 
WE8ISO8859P9 ISO 8859-9 West European & Turkish 
NE8ISO8859P10 ISO 8859-10 North European 
TH8TISASCII Thai Industrial Standard 620-2533 - ASCII 8-bit 
TH8TISEBCDIC Thai Industrial Standard 620-2533 - EBCDIC 8-bit 
AR8EBCDICX EBCDIC XBASIC 8-bit Latin/Arabic 
EL8DEC DEC 8-bit Latin/Greek 
TR8DEC DEC 8-bit Turkish 
WE8EBCDIC37C EBCDIC Code Page 37 8-bit Oracle/c 
RU8PC866 IBM-PC Code Page 866 8-bit Latin/Cyrillic 
WE8EBCDIC500C EBCDIC Code Page 500 8-bit Oracle/c 
EEC8EUROPA3 EEC EUROPA3 8-bit West European/Greek 
EE8PC852 IBM-PC Code Page 852 8-bit East European 
RU8BESTA BESTA 8-bit Latin/Cyrillic 
RU8PC855 IBM-PC Code Page 855 8-bit Latin/Cyrillic 
TR8PC857 IBM-PC Code Page 857 8-bit Turkish 
CL8MACCYRILLIC Mac Client 8-bit Latin/Cyrillic 
CL8MACCYRILLICS Mac Server 8-bit Latin/Cyrillic 
WE8PC860 IBM-PC Code Page 860 8-bit West European 
IS8PC861 IBM-PC Code Page 861 8-bit Icelandic 
EE8MACCES Mac Server 8-bit Central European 
EE8MACCROATIANS Mac Server 8-bit Croatian 
TR8MACTURKISHS Mac Server 8-bit Turkish 
IS 8MACICELANDICS Mac Server 8-bit Icelandic 
EL8MACGREEKS Mac Server 8-bit Greek 
EE8MSWIN 1250 MS Windows Code Page 1250 8-bit East European 
CL8MSWIN1251 MS Windows Code Page 1251 8-bit Latin/Cyrillic 
F8EBCDIC297 EBCDIC Code Page 297 8-bit French 
BG8MSWIN MS Windows 8-bit Bulgarian Cyrillic 
EL8MSWIN1253 MS Windows Code Page 1253 8-bit Latin/Greek 
D8EBCDIC273 EBCDIC Code Page 273/18-bit Austrian German 
I8EBCDIC280 EBCDIC Code Page 280/18-bit Italian 
DK8EBCDIC277 EBCDIC Code Page 277/18-bit Danish 
S8EBCDIC278 EBCDIC Code Page 278/18-bit Swedish 
EE8EBCDIC870 EBCDIC Code Page 870 8-bit East European 
CL8EBCDIC1025 EBCDIC Code Page 1025 8-bit Cyrillic 
N8PC865 IBM-PC Code Page 865 8-bit Norwegian 
F7SIEMENS9780X Siemens 97801/97808 7-bit French 
E7SIEMENS9780X Siemens 97801/97808 7-bit Spanish 
S7SIEMENS9780X Siemens 97801/97808 7-bit Swedish 
DK7SIEMENS9780X Siemens 97801/97808 7-bit Danish 
N7SIEMENS9780X Siemens 97801/97808 7-bit Norwegian 
I7SIEMENS9780X Siemens 97801/97808 7-bit Italian 
D7SIEMENS9780X Siemens 97801/97808 7-bit German 
WE8GCOS7 Bull EBCDIC GCOS7 8-bit West European 
US8BS2000 Siemens 9750-62 EBCDIC 8-bit American 
D8BS2000 Siemens 9750-62 EBCDIC 8-bit German 
F8BS2000 Siemens 9750-62 EBCDIC 8-bit French 
E8BS2000 Siemens 9750-62 EBCDIC 8-bit Spanish 
DK8BS2000 S Siemens 9750-62 EBCDIC 8-bit Danish 
WE8BS2000 Siemens EBCDIC.DF.04 8-bit West European 
CL8BS2000 Siemens EBCDIC.EHC.LC 8-bit Cyrillic 
WE8BS2000L5 Siemens EBCDIC.DF.O4.L5 8-bit West European/Turkish 
WE8DG DG 8-bit West European 
WE8NCR4970 NCR 4970 8-bit West European 
WE8ROMAN8 HP Roman8 8-bit West European 
EE8MACCE Mac Client 8-bit Central European 
EE8MACCROATIAN Mac Client 8-bit Croatian 
TR8MACTURKISH Mac Client 8-bit Turkish 
IS8MACICELANDIC Mac Client 8-bit Icelandic 
EL8MACGREEK Mac Client 8-bit Greek 
US8ICL ICL EBCDIC 8-bit American 
WE8ICL ICL EBCDIC 8-bit West European 
WE8MACROMAN8 Mac Client 8-bit Extended Roman8 West European 
WE8MACROMAN8S Mac Server 8-bit Extended Roman8 West European 
TH8MACTHAI Mac Client 8-bit Latin/Thai 
TH8MACTHAIS Mac Server 8-bit Latin/Thai 
HU8CWI2 Hungarian 8-bit CWI-2 
TR8ISO8859P9 Turkish version ISO 8859-9 West European & Turkish 
EL8PC437S IBM-PC Code Page 437 8-bit (Greek modification) 
EL8EBCDIC875 EBCDIC Code Page 875 8-bit Greek 
EL8PC737 IBM-PC Code Page 737 8-bit Greek/Latin 
LT8PC772 IBM-PC Code Page 772 8-bit Lithuanian (Latin/Cyrillic) 
LT8PC774 IBM-PCCode Page 774 8-bit Lithuanian (Latin) 
CDN8PC863 IBM-PC Code Page 863 8-bit Canadian French 
AR8ASMO8X ASMO Extended 708 8-bit Latin/Arabic 
AR8NAFITHA711 Nafitha Enhanced 711 Server 8-bit Latin/Arabic 
AR8SAKHR707 SAKHR 707 Server 8-bit Latin/Arabic 
AR8MUSSAD768 Mussa'd Alarabi/2 768 Server 8-bit Latin/Arabic 
AR8ADOS710 Arabic MS-DOS 710 Server 8-bit Latin/Arabic 
AR8ADOS720 Arabic MS-DOS 720 Server 8-bit Latin/Arabic 
AR8APTEC715 APTEC 715 Server 8-bit Latin/Arabic 
AR8MSWIN1256 MS Windows Code Page 1256 8-Bit Latin/Arabic 
AR8NAFITHA721 Nafitha International 721 Server 8-bit Latin/Arabic 
AR8SAKHR706 SAKHR 706 Server 8-bit Latin/Arabic 
AR8ARABICMAC Mac Client 8-bit Latin/Arabic 
AR8ARABICMACS Mac Server 8-bit Latin/Arabic 
JA16VMS JVMS 16-bit Japanese 
JA16EUC EUC 16-bit Japanese 
JA16SJIS Shift-JIS 16-bit Japanese 
JA16DBCS IBM DBCS 16-bit Japanese 
JA16HP HP 16-bit Japanese 
JA16EBCDIC930 IBM DBCS Code Page 290 16-bit Japanese 
JA16TOSHIBAEUC Toshiba EUC 16-bit Japanese 
KO16KSC5601 KSC5601 16-bit Korean 
KO16DBCS IBM DBCS 16-bit Korean 
ZHS16CGB231280 CGB2312-80 16-bit Simplified Chinese 
ZHT32EUC EUC 32-bit Traditional Chinese 
ZHT32SOPS SOPS 32-bit Traditional Chinese 
ZHT16DBT Taiwan Taxation 16-bit Traditional Chinese 
ZHT32TRIS TRIS 32-bit Traditional Chinese 
ZHT16BIG5 BIG5 16-bit Traditional Chinese 
AL24UTFFSS Unicode UTF-FSS
JA16TSTSET2 ASCII-based 16-bit Test Character Set 
JA16TSTSET Shift-sensitive ASCII-based Test Character Set 
Table 4 - 2. (continued) Storage Character Sets

Arabic/Hebrew Display Character Sets
The following Arabic/Hebrew display character sets are supported in Oracle Server release 7.3: 
Name Description 
AR8ASMO708PLUS ASMO 708 Plus 8-bit Latin/Arabic 
AR7ASMO449PLUS ASMO 449 Plus 7-bit Latin/Arabic 
AR7AMEER Ameer 7-bit Latin/Arabic 
AR8XBASIC XBASIC Right-to-Left Arabic Character Set 
AR8NAFITHA711T Nafitha Enhanced 711 Client 8-bit Latin/Arabic 
AR8SAKHR707T SAKHR 707 Client 8-bit Latin/Arabic 
AR8MUSSAD768T Mussa'd Alarabi/2 768 Client 8-bit Latin/Arabic 
AR8ADOS710T Arabic MS-DOS 710 Client 8-bit Latin/Arabic 
AR8ADOS720T Arabic MS-DOS 720 Client 8-bit Latin/Arabic 
AR8APTEC715T APTEC 7 15 Client 8-bit Latin/Arabic 
AR8NAFITHA721T Nafitha International 721 Client 8-bit Latin/Arabic 
AR7SEDCOT SEDCO/ESPRIT/DATA GENERAL 7-bit Latin/Arabic 
AR8HPARABIC8T HP ARABIC8 8-bit Latin/Arabic 
_____________________________________________________________________
 
摘要至itpub
AL16UTF16 和 UTF8 这两种选择都适用于国家字符集
AL16UFT16 是宽度固定的双字节 Unicode 字符集

UTF8 是宽度可变的、一至三个字节的 Unicode 字符集
欧洲字符在 UTF8 中按一至两个字节存储，而在 AL16UTF16 中按两个字节存储，相比之下，UTF8可以节省空间
亚洲字符在 UTF8 中按三个字节存储，这样，所需的空间比在 AL16UTF16 中要多

AL16UTF16 是宽度固定的编码，因此在执行速度上要比宽度可变的 UTF8 快
 
翻译的一段：   
    
  字符集类型   
    
          CREATE   DATABASE语句中有CHARACTER   SET从句和附加的NATIONAL   CHARACTER   SET从句用来定义   
  数据库的字符集和国家字符集。这两个字符集在数据库创建之后都无法修改。如果不指明NATIONAL   
  CHARACTER   SET从句，则国家字符集缺省取数据库字符集。   
          因为数据库字符集用于标识并装载SQL和PL/SQL源代码，所以数据库字符集必须将EBCDIC或7位ASCII   
  作为子集。因此，固定宽度，多字节字符集不可能作为数据库字符集，而只能作为国家字符集。数据类型   
  NCHAR,NVARCHAR2和NCLOB是基本数据类型CHAR,VARCHAR2和BLOB的变体，来指明它们用国家字符集而   
  不是数据库字符集存储数据。   
    
        NCHAR用于使用国家字符集定义固定长度的字符项。   
        NVARCHAR2用于使用国家字符集定义变长度的字符项。   
        NCLOB用于使用国家字符集定义字符大对象，来保存固定宽度，多字节字符。   
    
        数据库字符集存储变宽度字符，国家字符集存储固定宽度和变宽度多字节字符。
 
 
原文   
    
  Character   Set   Types   
  The   CREATE   DATABASE   statement   has   the   CHARACTER   SET   clause   and   the   
  additional   optional   clause   NATIONAL   CHARACTER   SET   to   declare   the   character   set   
  to   be   used   as   the   database   character   set   and   the   national   character   set.   Neither   
  character   set   can   be   changed   after   creating   the   database.   If   no   NATIONAL   
  CHARACTER   SET   clause   is   present,   the   national   character   set   defaults   to   the   
  database   character   set.   
  Because   the   database   character   set   is   used   to   identify   and   to   hold   SQL   and   PL/SQL   
  source   code,   it   must   have   either   EBCDIC   or   7-bit   ASCII   as   a   subset,   whichever   is   
  native   to   the   platform.   Therefore,   it   is   not   possible   to   use   a   fixed-width,   multibyte   
  character   set   as   the   database   character   set,   only   as   the   national   character   set.   
  The   data   types   NCHAR,   NVARCHAR2,   and   NCLOB   are   provided   to   declare   columns   
  as   variants   of   the   basic   types   CHAR,   VARCHAR2,   and   CLOB,   to   note   that   they   are   
  stored   using   the   national   character   set   and   not   the   database   character   set.   
  •   To   declare   a   fixed-length   character   item   that   uses   the   national   character   set,   use   the   
  data   type   specification   NCHAR   [(size)].   
  •   To   declare   a   variable-length   character   item   that   uses   the   national   character   set,   use   
  the   data   type   specification   NVARCHAR2   (size).   
  •   To   declare   a   character   large   object   (CLOB)   item   containing   fixed-width,   multibyte   
  characters   that   uses   the   national   character   set,   use   the   data   type   specification   
  NCLOB   (size).
 
效率
　　从上述编码原理中得出的结论是：
　　1.每个英文字母、数字所占的空间为1 Byte；
　　2.泛欧语系、斯拉夫语字母占2 Bytes；
　　3.汉字占3 Bytes。
　　由此可见UTF8对英文来说是个非常诱人的方案，但对中文来说则不太合算，无论用ANSI还是 Unicode/UCS2来编码都只用2 Bytes，但用UTF8则需要3 Bytes。
　　以下是一些统计资料，显示用UTF8来储存文件每个字符所需的平均字节：
　　1.拉丁语系平均用1.1 Bytes；
　　2.希腊文、俄文、阿拉伯文和希伯莱文平均用1.7 Bytes；
　　3.其他大部份文字如中文、日文、韩文、Hindi(北印度语)用约3 Bytes；
　　4.用超过4 Bytes的都是些非常少用的文字符号。
 
 
 
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