>not getting results required from joining table to itself i.e.

My crystal ball is in the shop for repair.
Give us a clue as to what exactly are your "required results".

Basically I need the proxy user to be the DBA_AUDIT_TRAIL.USERNAME

And explain what is the purpose of "WHERE A.PROXY_SESSIONID = B.SESSIONID"?

I fail to see what you want to get.

USERNAME	ACTION_NAME	            SESSIONID	PROXY_SESSIONID
PROXYONE	PROXY AUTHENTICATION ONLY   80022050	
GENERIC	        LOGON	                    80022051	80022050
GENERIC	        CREATE TABLE	            80022051	80022050
GENERIC	        CREATE TABLE	            80022051	80022050
GENERIC	        CREATE TABLE	            80022051	80022050
GENERIC	        LOGOFF	                    80022051	80022050

Quote:

Basically I need the proxy user to be the DBA_AUDIT_TRAIL.USERNAME

You have in this column what Oracle puts in it.
If this is not what you want refer to Oracle.

I still fail to see what you want.
Put a CLEAR example.

And from the example you gave, what should be the result?

And from the example you gave, what should be the result?

You just need to enable te audit of the proxy. For example,

audit select table on emp by scott on behalf of fred;

--update: sorry, I had slightly wrong syntax. You can't audit access to a table, only use of a privilege.
So it would have to be:
audit select table by scott on behalf of fred;