group time by hour sql code example

Example: oracle sql group by date year

Select count(1), country_of_sale, to_char(datefield, 'YYYY-MM') AS yyyymm
from table 
where country_of_sale IN ('USA', 'EUROPE', 'ASIA')
group by country_of_sale, to_char(datefield, 'YYYY-MM')
order by to_char(datefield, 'YYYY-MM');