Question

INSERT INTO PHOENIX_AUDITTRAIL SET
audit_module = 'Location Master',
audit_message = 'Delete location',
datecreated = NOW(),
author = '".$_SESSION['username']."',
status = '".ADT_NOTICE."';

Answer 1

No, the standard way to phrase this is:

INSERT INTO PHOENIX_AUDITTRAIL(audit_module, audit_message, datecreated, author, status)
    select 'Location Master', 'Delete location', NOW(), '".$_SESSION['username']."', '".ADT_NOTICE."'
    from dual

However, in Oracle, I think you would use sysdate instead of now():

INSERT INTO PHOENIX_AUDITTRAIL(audit_module, audit_message, datecreated, author, status)
    select 'Location Master', 'Delete location', sysdate, '".$_SESSION['username']."', '".ADT_NOTICE."'
    from dual

Except for the date variables and the from dual, this is standard SQL syntax.