自从选用了AL32UTF8字符集做为生产数据库字符集之后，就一直奔走于“乱码”与“转码”之间。
在与“乱码”PK良久之后，有了这个小文儿。
如果想要搞清楚Oracle的字符系统，需要紧紧地抓住三个因素：
一.“客户终端字符集”
二.“NLS_LANG”环境变量
三.“数据库字符集”
如果“NLS_LANG”等于“数据库字符集”时，不需要进行任何转换，直接把字符插入数据库
如果“NLS_LANG”不等于“数据库字符集”，则需要进行转换，乱码的根源就在这里
1.“数据库字符集”是AL32UTF8，具体信息如下：
sys@ora10g> col VALUE for a30
sys@ora10g> select * from nls_database_parameters;
PARAMETER VALUE
------------------------------ ------------------------------
NLS_LANGUAGE AMERICAN
NLS_TERRITORY AMERICA
NLS_CURRENCY $
NLS_ISO_CURRENCY AMERICA
NLS_NUMERIC_CHARACTERS .,
NLS_CHARACTERSET AL32UTF8
NLS_CALENDAR GREGORIAN
NLS_DATE_FORMAT DD-MON-RR
NLS_DATE_LANGUAGE AMERICAN
NLS_SORT BINARY
NLS_TIME_FORMAT HH.MI.SSXFF AM
NLS_TIMESTAMP_FORMAT DD-MON-RR HH.MI.SSXFF AM
NLS_TIME_TZ_FORMAT HH.MI.SSXFF AM TZR
NLS_TIMESTAMP_TZ_FORMAT DD-MON-RR HH.MI.SSXFF AM TZR
NLS_DUAL_CURRENCY $
NLS_COMP BINARY
NLS_LENGTH_SEMANTICS BYTE
NLS_NCHAR_CONV_EXCP FALSE
NLS_NCHAR_CHARACTERSET UTF8
NLS_RDBMS_VERSION 10.2.0.3.0
20 rows selected.
2.“客户终端字符集”信息如下：
以下实验使用了两种主要客户端（不包括后面提到的PL/SQL Developer和Toad）：一个是XP的cmd命令行工具，另一个是PuTTY工具。
1）XP字符集是
C:\>chcp
Active code page: 936
代码页936就是中文字符集GBK，可以参考msdn的资料《Windows Codepage 936》
http://www.microsoft.com/globaldev/reference/dbcs/936.htm
2）PuTTY字符集我的设置：utf8
3.客户端使用AL32UTF8字符集进行测试
C:\>set NLS_LANG=AMERICAN_AMERICA.AL32UTF8
C:\>sqlplus sec/sec@DB_AL32UTF8
SQL*Plus: Release 10.2.0.1.0 - Production on Tue Sep 22 16:12:14 2009
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bit Production
With the Partitioning, Oracle Label Security, OLAP and Data Mining Scoring Engine options
sec@ora10g> drop table t purge;
Table dropped.
sec@ora10g> create table t (x varchar2(20), y varchar2(20));
Table created.
sec@ora10g> insert into t values ('圣','AL32UTF8');
1 row created.
sec@ora10g> commit;
Commit complete.
sec@ora10g> col x for a10
sec@ora10g> col dump(x) for a30
sec@ora10g> select x, y, dump(x) from t;
X Y DUMP(X)
---------- -------------------- ------------------------------
圣 AL32UTF8 Typ=1 Len=2: 202,165
4.客户端使用WE8ISO8859P1字符集进行测试
C:\>set NLS_LANG=AMERICAN_AMERICA.WE8ISO8859P1
C:\>sqlplus sec/sec@DB_AL32UTF8
SQL*Plus: Release 10.2.0.1.0 - Production on Tue Sep 22 16:14:55 2009
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bit Production
With the Partitioning, Oracle Label Security, OLAP and Data Mining Scoring Engine options
sec@ora10g> insert into t values ('圣','WE8ISO8859P1');
1 row created.
sec@ora10g> commit;
Commit complete.
sec@ora10g>
sec@ora10g> col x for a10
sec@ora10g> col dump(x) for a30
sec@ora10g> select x, y, dump(x) from t;
X Y DUMP(X)
---------- -------------------- ------------------------------
AL32UTF8 Typ=1 Len=2: 202,165
圣 WE8ISO8859P1 Typ=1 Len=4: 195,138,194,165
5.客户端使用ZHS16GBK字符集进行测试
C:\>set NLS_LANG=AMERICAN_AMERICA.ZHS16GBK
C:\>sqlplus sec/sec@DB_AL32UTF8
SQL*Plus: Release 10.2.0.1.0 - Production on Tue Sep 22 16:17:13 2009
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bit Production
With the Partitioning, Oracle Label Security, OLAP and Data Mining Scoring Engine options
sec@ora10g> insert into t values ('圣','ZHS16GBK');
1 row created.
sec@ora10g> commit;
Commit complete.
sec@ora10g> col x for a10
sec@ora10g> col dump(x) for a30
sec@ora10g> select x, y, dump(x) from t;
X Y DUMP(X)
---------- -------------------- ------------------------------
？ AL32UTF8 Typ=1 Len=2: 202,165
ê￥ WE8ISO8859P1 Typ=1 Len=4: 195,138,194,165
圣 ZHS16GBK Typ=1 Len=3: 229,156,163
6.使用PuTTY以ssh方式连接数据库服务器进行测试
ora10g@secDB /home/oracle$ sqlplus sec/sec
SQL*Plus: Release 10.2.0.3.0 - Production on Tue Sep 22 16:21:17 2009
Copyright (c) 1982, 2006, Oracle. All Rights Reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bit Production
With the Partitioning, Oracle Label Security, OLAP and Data Mining Scoring Engine options
sec@ora10g> insert into t values ('圣','PuTTY AL32UTF8');
1 row created.
sec@ora10g> commit;
Commit complete.
sec@ora10g> col x for a10
sec@ora10g> col dump(x) for a30
sec@ora10g> select x, y, dump(x) from t;
X Y DUMP(X)
---------- -------------------- ------------------------------
? AL32UTF8 Typ=1 Len=2: 202,165
ê￥ WE8ISO8859P1 Typ=1 Len=4: 195,138,194,165
圣 ZHS16GBK Typ=1 Len=3: 229,156,163
圣 PuTTY AL32UTF8 Typ=1 Len=3: 229,156,163
7.后我们将NLS_LANG置空进行一下后的尝试
C:\>set NLS_LANG=
C:\>sqlplus sec/sec@DB_AL32UTF8
SQL*Plus: Release 10.2.0.1.0 - Production on Tue Sep 22 16:24:57 2009
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bit Production
With the Partitioning, Oracle Label Security, OLAP and Data Mining Scoring Engine options
sec@ora10g> insert into t values ('圣','unset NLS_LANG');
1 row created.
sec@ora10g> commit;
Commit complete.
sec@ora10g> col x for a10
sec@ora10g> col dump(x) for a30
sec@ora10g> select x, y, dump(x) from t;
X Y DUMP(X)
---------- -------------------- ------------------------------
圣 AL32UTF8 Typ=1 Len=2: 202,165
脢楼 WE8ISO8859P1 Typ=1 Len=4: 195,138,194,165
鍦? ZHS16GBK Typ=1 Len=3: 229,156,163
鍦? PuTTY AL32UTF8 Typ=1 Len=3: 229,156,163
圣 unset NLS_LANG Typ=1 Len=2: 202,165
8.Toad中“Execute as script”的执行效果：
X Y DUMP(X)
---------- -------------------- ------------------------------
? AL32UTF8 Typ=1 Len=2: 202,165
ê￥ WE8ISO8859P1 Typ=1 Len=4: 195,138,194,165
圣 ZHS16GBK Typ=1 Len=3: 229,156,163
圣 PuTTY AL32UTF8 Typ=1 Len=3: 229,156,163
? unset NLS_LANG Typ=1 Len=2: 202,165
5 rows selected.
9.Toad中“F9”的执行效果：
X Y DUMP(X)
---------- -------------------- ------------------------------
圣 AL32UTF8 Typ=1 Len=2: 202,165
脢楼 WE8ISO8859P1 Typ=1 Len=4: 195,138,194,165
鍦 ZHS16GBK Typ=1 Len=3: 229,156,163
鍦 PuTTY AL32UTF8 Typ=1 Len=3: 229,156,163
圣 unset NLS_LANG Typ=1 Len=2: 202,165
10.PL/SQL Developer中“Command Window”执行效果
X Y DUMP(X)
---------- -------------------- ------------------------------
? AL32UTF8 Typ=1 Len=2: 202,165
ê￥ WE8ISO8859P1 Typ=1 Len=4: 195,138,194,165
圣 ZHS16GBK Typ=1 Len=3: 229,156,163
圣 PuTTY AL32UTF8 Typ=1 Len=3: 229,156,163
? unset NLS_LANG Typ=1 Len=2: 202,165
11.PL/SQL Developer中“F8”执行效果
X Y DUMP(X)
---------- -------------------- ------------------------------
? AL32UTF8 Typ=1 Len=2: 202,165
ê￥ WE8ISO8859P1 Typ=1 Len=4: 195,138,194,165
圣 ZHS16GBK Typ=1 Len=3: 229,156,163
圣 PuTTY AL32UTF8 Typ=1 Len=3: 229,156,163
? unset NLS_LANG Typ=1 Len=2: 202,165
12.实验结论
1）如果有可能，尽量保证客户端编码（Windows XP的cmd工具可以使用chcp命令来确认）、NLS_LANG参数和数据库字符集这三个内容一致，这样设置，无论是从性能上，还是从防止编码转换上都是佳的；
2）如果目的是支持中文，数据库Server端的字符集应该尽量选择ZHS16GBK或AL32UTF8字符集，这样可以减少因不当的“转码”导致的字符乱码故障；
3）（推荐）可已将NLS_LANG参数与操作终端字符编码一致，这样可以保证数据库能正确获得应用终端使用的编码，这时会发生“编码转换”，但是，这样就可以保证正确转码，可以防止错误的编码存入数据库；
4）（不推荐）也可以将NLS_LANG参数与数据库服务器端的编码一致，这样，客户端无论是发送到服务器端还是从服务器接收数据都不会“转码”，这样能保证客户端对字符的显示效果，但是，一定要小心，这时数据库服务器上存放的字符编码很可能是错误的。
5）PL/SQL Developer工具在AL32UTF8字符集下貌似可以保证数据效果，但是“Toad同学”貌似不太“稳定”。
secooler
09.09.22
-- The End --
【字符集】“客户终端字符集”、“NLS_LANG”环境变量以及“数据库字符集”
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