How many unique competition types are there?
select count (distinct competition_type) from competition
How many competitions are there for each type?
select competition_type, count(*) from competition group by competition_type
What are the top 3 competition types?
select competition_type from competition group by competition_type order by count(*) desc limit 3
What about the ones that have at most five competitions of that type.
select competition_type from competition group by competition_type having count(*) <= 5