select sum(sum_amount), footype
from (
	select sum(amount) as sum_amount, footype
	from db1.foo
	group by footype
	UNION ALL
	select sum(amount) as sum_amount, footype
	from db2.foo
	group by footype
	UNION ALL
	...
	UNION ALL
	select sum(amount) as sum_amount, footype
	from dbN.foo
	group by footype
)
group by footype