- Average_population - Solution
- Japan_population - Solution
- Population_density_difference - Solution
- Revising_aggregations_-_averages - Solution
- Revising_aggregations_-_sum - Solution
- Revising_aggregations_-_the_count_function - Solution
- The_blunder - Solution
- Top_earners - Solution
- Weather_observation_station_II - Solution
- Weather_observation_station_XIII - Solution
- Weather_observation_station_XIV - Solution
- Weather_observation_station_XV - Solution
- Weather_observation_station_XVI - Solution
- Weather_observation_station_XVII - Solution
- Weather_observation_station_XVIII - Solution
- Weather_observation_station_XIX - Solution
- Weather_observation_station_XX - Solution
- African_cities - Solution
- Average_population_of_each_continent - Solution
- Challenges - Solution
- Contest_Leaderboard - Solution
- Ollivanders_Inventory - Solution
- Population_census - Solution
- The_Competitors - Solution
- The_Report - Solution
- Employee_salaries - Solution
- Higher_than_75_marks - Solution
- Japanese_cities_attributes - Solution
- Japanese_cities_names - Solution
- Name_of_employees - Solution
- Revising_the_select_query_I - Solution
- Revising_the_select_query_II - Solution
- Select_all - Solution
- Select_by_ID - Solution
- Weather_observation_station_I - Solution
- Weather_observation_station_III - Solution
- Weather_observation_station_IV - Solution
- Weather_observation_station_V - Solution
- Weather_observation_station_VI - Solution
- Weather_observation_station_VII - Solution
- Weather_observation_station_VIII - Solution
- Weather_observation_station_IX - Solution
- Weather_observation_station_X - Solution
- Weather_observation_station_XI - Solution
- Weather_observation_station_XII - Solution