codice:
SELECT c.cust_id,c.azienda,
sum(if(year(data_ordine)=2007,totale,0)) as '2007',
sum(if(year(data_ordine)=2008,totale,0)) as '2008',
sum(if(year(data_ordine)=2009,totale,0)) as '2009'
FROM  clienti c, ordini o 
WHERE c.cust_id = o.cust_id 
GROUP BY c.cust_id