Weather Observation Station 3 & Weather Observation Station 4 (hackerRank)

Weather Observation Station 3

https://www.hackerrank.com/challenges/weather-observation-station-3/problem?isFullScreen=true

SELECT DISTINCT city
FROM station
WHERE id % 2 = 0

Weather Observation Station 4

https://www.hackerrank.com/challenges/weather-observation-station-4/problem?isFullScreen=true

SELECT count(city) - count(DISTINCT(city))
FROM station