SQL

I will post medium and hard query of sql on hackerrank

Name		Name	Last commit message	Last commit date
Latest commit History 12 Commits
LICENSE		LICENSE
README.md		README.md
african-cities		african-cities
more-than-75-marks		more-than-75-marks
weather-observation-station-10		weather-observation-station-10
weather-observation-station-11		weather-observation-station-11
weather-observation-station-12		weather-observation-station-12
weather-observation-station-4		weather-observation-station-4
weather-observation-station-6		weather-observation-station-6
weather-observation-station-7		weather-observation-station-7
weather-observation-station-8		weather-observation-station-8
weather-observation-station-9		weather-observation-station-9

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