lark the query has the same result... Joachim is right! Is an
alphabetic order and not numerical....
i'm try to do this

select prova,risoluzione, inizio, timediff(risoluzione,inizio) as
delta
from statistiche
where (prova=1 and risoluzione is not null)
order by cast (delta as int) // or datetime but doesn't works...

any idea?