Risolto.

codice:
select year(datas) as anno,
sum(if(month(datas) = 1,1,0)) as gen,
sum(if(month(datas) = 2,1,0)) as feb,
sum(if(month(datas) = 3,1,0)) as mar,
sum(if(month(datas) = 4,1,0)) as apr,
sum(if(month(datas) = 5,1,0)) as mag,
sum(if(month(datas) = 6,1,0)) as giu,
sum(if(month(datas) = 7,1,0)) as lug,
sum(if(month(datas) = 8,1,0)) as ago,
sum(if(month(datas) = 9,1,0)) as sett,
sum(if(month(datas) = 10,1,0)) as ott,
sum(if(month(datas) = 11,1,0)) as nov,
sum(if(month(datas) = 12,1,0)) as dic
from messaggi
group by anno