column OS_USERNAME format a20
column USERNAME  format a30
column USERHOST format a30
column action  format 999999
column returncode format 999999
column timestamp  format a20


select OS_USERNAME,USERNAME,USERHOST,action,action_name,returncode,to_char(timestamp,'ddmmyyyy hh24:mi:ss') timestamp
from (
select OS_USERNAME,USERNAME,USERHOST,action,action_name,returncode,timestamp
from dba_audit_trail
where username like upper('%&1%'))
where rownum < 20
order by timestamp desc;