To extract Country wise sales count for the period MAY-2010 use below code.
Select c.country_name, count(s.id) from tbl_sales s inner join tbl_country c on s.country_id=c.country_id where s.saels_date between '2010-05-01 00:00:00' and '2010-05-31 23:59:59' group by c.coutnry_name
