Oracle一个中文汉字占用几个字节，要根据Oracle中字符集编码决定。

--查看oracle server端字符集

select userenv('language') from dual;

--如果显示如下，一个汉字占用两个字节

--SIMPLIFIED CHINESE_CHINA.ZHS16GBK

--如果显示如下，一个汉字占用三个字节

--SIMPLIFIED CHINESE_CHINA.AL32UTF8

--可以用以下语句查询一个汉字占用的字节长度

select lengthb('你') from dual;

--VSIZE(X) 返回X的大小(字节)数

select vsize(user),user from dual;

--sys_context

select SYS_CONTEXT('USERENV', 'TERMINAL') terminal,

SYS_CONTEXT('USERENV', 'LANGUAGE') language,

SYS_CONTEXT('USERENV', 'SESSIONID') sessionid,

SYS_CONTEXT('USERENV', 'INSTANCE') instance,

SYS_CONTEXT('USERENV', 'ENTRYID') entryid,

SYS_CONTEXT('USERENV', 'ISDBA') isdba,

SYS_CONTEXT('USERENV', 'NLS_TERRITORY') nls_territory,

SYS_CONTEXT('USERENV', 'NLS_CURRENCY') nls_currency,

SYS_CONTEXT('USERENV', 'NLS_CALENDAR') nls_calendar,

SYS_CONTEXT('USERENV', 'NLS_DATE_FORMAT') nls_date_format,

SYS_CONTEXT('USERENV', 'NLS_DATE_LANGUAGE') nls_date_language,

SYS_CONTEXT('USERENV', 'NLS_SORT') nls_sort,

SYS_CONTEXT('USERENV', 'CURRENT_USER') current_user,

SYS_CONTEXT('USERENV', 'CURRENT_USERID') current_userid,

SYS_CONTEXT('USERENV', 'SESSION_USER') session_user,

SYS_CONTEXT('USERENV', 'SESSION_USERID') session_userid,

SYS_CONTEXT('USERENV', 'PROXY_USER') proxy_user,

SYS_CONTEXT('USERENV', 'PROXY_USERID') proxy_userid,

SYS_CONTEXT('USERENV', 'DB_DOMAIN') db_domain,

SYS_CONTEXT('USERENV', 'DB_NAME') db_name,

SYS_CONTEXT('USERENV', 'HOST') host,

SYS_CONTEXT('USERENV', 'OS_USER') os_user,

SYS_CONTEXT('USERENV', 'EXTERNAL_NAME') external_name,

SYS_CONTEXT('USERENV', 'IP_ADDRESS') ip_address,

SYS_CONTEXT('USERENV', 'NETWORK_PROTOCOL') network_protocol,

SYS_CONTEXT('USERENV', 'BG_JOB_ID') bg_job_id,

SYS_CONTEXT('USERENV', 'FG_JOB_ID') fg_job_id,

SYS_CONTEXT('USERENV', 'AUTHENTICATION_TYPE') authentication_type,

SYS_CONTEXT('USERENV', 'AUTHENTICATION_DATA') authentication_data

from dual;

一个汉字占2个字节：

一个汉字占3个字节：