Oracle Differences

What is the Difference between SYSDATE and CURRENT_DATE ?

                                SYSDATE returns the date from the Server where the Instance is Running.

                                CURRENT_DATE returns the date using the Session.

What is the Difference between LOG and LN ?

                                LN = log base e

                                LOG = log base 10.

What is the difference between NANVL and NVL ?

                                NANVL : Numeric Function. Only Deals with Floating, Binary_Float values + NAN.

                                NVL:     Character Function. Deals with String, expression.

What is the Difference between LOCALTIMESTAMP , CURRENTTIMESTAMP and SYSTIMESTAMP ?

                                LOCALTIMESTAMP:    SESSION TIME STAMP

                                CURRENTTIMESTAMP:              SESSION TIME STAMP WITH TIMEZONE

                                SYSTIMESTAMP:                           SERVER TIME STAMP WITH TIME ZONE

NEWTIME is not working.

                                ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY HH24:MI:SS';

                                SELECT NEW_TIME(TO_DATE('11-10-99 01:23:45', 'MM-DD-YY HH24:MI:SS'),'AST', 'PST') "New Date and Time" FROM DUAL;