一、server 端 字符集查询

select userenv(‘language’) from dual
其中NLS_CHARACTERSET 为server端字符集

NLS_LANGUAGE 为 server端字符显示形式
二、查询oracle client端的字符集

$echo $NLS_LANG
如果发现你select 出来的数据是乱码，请把client端的字符集配置成与linux操作系统相同的字符集。如果还是有乱码，则有可能是数据库中的数据存在问题，或者是oracle服务端的配置存在问题。

三、server端字符集修改
更改字符集步骤方法(AL32UTF8–> ZHS16GBK)

开始 - 运行 - 输入cmd 进入命令提示符

输入 sqlplus /nolog

以管理员身份登录sqlplus

SQL> conn /as sysdba

Connected.

SQL> shutdown immediate;

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> startup mount

ORACLE instance started.

Total System Global Area 236000356 bytes

Fixed Size 451684 bytes

Variable Size 201326592 bytes

Database Buffers 33554432 bytes

Redo Buffers 667648 bytes

Database mounted.

SQL> ALTER SYSTEM ENABLE RESTRICTED SESSION;

System altered.

SQL> ALTER SYSTEM SET JOB_QUEUE_PROCESSES=0;

System altered.

SQL> ALTER SYSTEM SET AQ_TM_PROCESSES=0;

System altered.

SQL> alter database open;

Database altered.

SQL> ALTER DATABASE CHARACTER SET ZHS16GBK;
ALTER DATABASE CHARACTER SET ZHS16GBK
ORA-12712: new character set must be a superset of old character set

提示我们的字符集：新字符集必须为旧字符集的超集，这时我们可以跳过超集的检查做更改：

SQL> ALTER DATABASE character set INTERNAL_USE ZHS16GBK;

Database altered.

SQL> select * from v$nls_parameters;

重启检查是否更改完成：

SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.

SQL> startup
ORACLE instance started.
Total System Global Area 236000356 bytes
Fixed Size 451684 bytes
Variable Size 201326592 bytes
Database Buffers 33554432 bytes
Redo Buffers 667648 bytes
Database mounted.
Database opened.
SQL> select * from v$nls_parameters;
19 rows selected.

四、修改环境变量

设置oracle用户的的环境
linux下修改环境变量（临时）
export NLS_LANG=“SIMPLIFIED Chinese_CHINA.ZHS16GBK”
如果是windows，按照以下方法添加或者修改，在系统变量中添加如下信息：
变量名：NLS_LANG
变量值：SIMPLIFIED Chinese_CHINA.ZHS16GBK