sys_context()函数用法解析

--sys_context

SYS_CONTEXT('namespace', 'parameter' [, length ])

SYS_CONTEXT returns the value of parameter associated with the context namespace at the current instant. You can use this function in both SQL and PL/SQL statements. SYS_CONTEXT must be executed locally.

The namespace must be a valid SQL identifier. The parameter name can be any string. It is not case sensitive, but it cannot exceed 30 bytes in length.

Oracle provides the following built-in namespaces:

USERENV - Describes the current session. The predefined parameters of namespace USERENV are listed in Table 5-11.

SYS_SESSION_ROLES - Indicates whether a specified role is currently enabled for the session. This namespace is available starting with Oracle Database 11g Release 2 (11.2.0.4).

parameter的值： http://docs.oracle.com/cd/E11882_01/server.112/e41084/functions184.htm#SQLRF06117
EODA@PROD1> select SYS_CONTEXT('USERENV','LANGUAGE') language from dual;

LANGUAGE
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AMERICAN_AMERICA.AL32UTF8

EODA@PROD1> select SYS_CONTEXT('USERENV','CURRENT_USER') current_user from dual;

CURRENT_USER
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EODA

EODA@PROD1> select sys_context('userenv', 'sid') from dual;

SYS_CONTEXT('USERENV','SID')
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50