To Calculate Diff. Shared memory by Oracle Process

SELECT
'PGA: pid '||p.spid pid,p.pga_alloc_mem bytes,
p.username ps_user,p.program ps_program,
s.logon_time,s.sid,s.serial#,s.username,s.machine,s.osuser,s.program
FROM v$session s ,v$sesstat pcur,v$process p WHERE pcur.statistic#=20 AND s.paddr=p.addr AND pcur.sid=s.sid
UNION ALL SELECT 'SGA: '||name pid,value bytes,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL FROM v$sga
ORDER BY 2 DESC