List the positions from all seasons.
select position from match_season
How many are there for each position?
select position, count(*) from match_season group by position
Show the positions and the corresponding country.
select t2.position,t1.country_name from country as t1 join match_season as t2 on t1.country_id = t2.country
Keep the country names that have both forward and defender as position.
select t1.country_name from country as t1 join match_season as t2 on t1.country_id = t2.country where t2.position = "Forward" intersect select t1.country_name from country as t1 join match_season as t2 on t1.country_id = t2.country where t2.position = "Defender"