1.USEREVN()

返回当前用户环境的信息,opt可以是:
ENTRYID,SESSIONID,TERMINAL,ISDBA,LABLE,LANGUAGE,CLIENT_INFO,LANG,VSIZE

1）ISDBA 查看当前用户是否是DBA如果是则返回true
SQL> select userenv('isdba') from dual;

USEREN
------
FALSE

2）SESSION 返回会话标志
SQL> select userenv('sessionid') from dual;

USERENV('SESSIONID')
--------------------
152

3）ENTRYID 返回会话人口标志
SQL> select userenv('entryid') from dual;

USERENV('ENTRYID')
------------------
0

4）INSTANCE 返回当前INSTANCE的标志
SQL> select userenv('instance') from dual;

USERENV('INSTANCE')
-------------------
1

5）LANGUAGE 返回当前环境变量
SQL> select userenv('language') from dual;

USERENV('LANGUAGE')
----------------------------------------------------
SIMPLIFIED CHINESE_CHINA.ZHS16GBK

6）LANG 返回当前环境的语言的缩写
SQL> select userenv('lang') from dual;

USERENV('LANG')
----------------------------------------------------
ZHS

7）TERMINAL 返回用户的终端或机器的标志
SQL> select userenv('terminal') from dual;

USERENV('TERMINA
----------------
GAO

8）VSIZE(X) 返回X的大小(字节)数
SQL> select vsize(user),user from dual;

VSIZE(USER) USER
----------- ------------------------------
6 SYSTEM

2.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;