Selecting from dual

Question

Does anyone have a list of all of the environment selections available from dual.
e.g. select user from dual;
Thanks in advance
Bob

Answer 1

Hi Bob,
there are a lot of usful selections possible using DUAL. For more
information I'd like to suggest you to look into SQL Reference Guide
chapter 4, which describes for example the powerful SYS_CONTEXT
function.
Regards,
Roland
Find attached some usful examples on using dual:
================================================
Current session:
================
SQL> select sid,serial#
from v$session
where audsid in (SELECT USERENV('SESSIONID') FROM DUAL);
SID SERIAL#
13 830
Which protocol is currently used for connection?
================================================
SQL> SELECT SYS_CONTEXT('USERENV','NETWORK_PROTOCOL') from dual;
SYS_CONTEXT('USERENV','NETWORK_PROTOCOL')
tcp
When nothing will be returned then you're using the BEQUEATH protocol.
(Session on loacal server that has connected without using a listener)
Which IP address will be used by session?
=========================================
SQL> SELECT SYS_CONTEXT('USERENV','IP_ADDRESS') "My IP Address" from dual;
My IP Address
140.84.134.14
Which NLS Environment will be used?
===================================
SQL> SELECT SYS_CONTEXT('USERENV','LANGUAGE') "nls_lang" from dual;
nls_lang
AMERICAN_AMERICA.WE8ISO8859P1