What about the weather
Regionally, Africa has a reputation for dominating in the field of running. However, Africa has the fewest athletes per (competing) country. Why?
Running events are only found in the Summer Olympics, so maybe Africa does not send many athletes to the Winter Games. This would explain the low number of athletes when looking across all Olympic Games.
Explore that hypothesis by looking at athlete counts by season (Summer versus Winter).
This exercise is part of the course
Improving Query Performance in PostgreSQL
Exercise instructions
- Add the
seasonfield from theathletestable to theSELECTstatement. - Choose the join type to return only countries with competing athletes.
- Sort by
regionandathletes_per_countryto see if there is a difference between the summer and Winter Olympics.
Hands-on interactive exercise
Have a go at this exercise by completing this sample code.
SELECT reg.region
, ___
, COUNT(DISTINCT ath.athlete_id) AS no_athletes
, COUNT(DISTINCT reg.olympic_cc) AS no_countries
, COUNT(DISTINCT ath.athlete_id)/COUNT(DISTINCT reg.olympic_cc) AS athletes_per_country
FROM athletes ath
___ JOIN oregions reg
ON ath.country_code = reg.olympic_cc
GROUP BY reg.region, ___ -- Group by region and season
___ ___ , ___;