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SELECT * FROM countries | |
LIMIT 5; | |
SELECT * FROM population_years | |
LIMIT 5; | |
--How many entries in the countries table are from Africa?-- | |
SELECT COUNT(name) FROM countries | |
WHERE continent = 'Africa'; | |
--Ans: 56 | |
--What was the total population of the continent of Oceania in 2005? | |
SELECT countries.continent, ROUND(SUM(population_years.population), 2) AS 'Oceania in 2005', population_years.year FROM countries | |
JOIN population_years | |
ON countries.id = population_years.country_id | |
WHERE countries.continent = 'Oceania' AND population_years.year = 2005; | |
--Ans: 32.66 | |
--What is the average population of countries in South America in 2003? | |
SELECT countries.continent, ROUND(AvG(population_years.population), 2) AS 'Avr in SA 2003', population_years.year FROM countries | |
JOIN population_years | |
ON countries.id = population_years.country_id | |
WHERE countries.continent = 'South America' AND population_years.year = 2003; | |
--Ans: 25.89 | |
--What country had the smallest population in 2007? | |
SELECT countries.name, population_years.population FROM countries | |
JOIN population_years | |
ON countries.id = population_years.country_id | |
WHERE population_years.year = 2007 AND population_years.population IS NOT NULL | |
ORDER BY population_years.population ASC | |
LIMIT 1; | |
--Ans: Niue, population 0.00216 | |
--What is the average population of Poland during the time period covered by this dataset? | |
SELECT ROUND(AVG(population_years.population), 2), countries.name FROM countries | |
JOIN population_years | |
ON countries.id = population_years.country_id | |
WHERE countries.name LIKE '%Poland%' AND population_years.year = 2010; | |
--Ans: 38.46 | |
--How many countries have the word “The” in their name? | |
SELECT *, COUNT(*) FROM countries | |
WHERE countries.name LIKE '%The%' | |
GROUP BY name; | |
SELECT COUNt(*) FROM countries | |
WHERE countries.name LIKE '%The%'; | |
--Ans:4 | |
--What was the total population of each continent in 2010? | |
SELECT countries.continent, ROUND(SUM(population_years.population), 2) AS 'All in 2010', population_years.year FROM countries | |
JOIN population_years | |
ON countries.id = population_years.country_id | |
WHERE population_years.year = 2010 | |
GROUP BY countries.continent | |
ORDER BY 2 DESc; | |
--Ans: Asia - 4133.09, Africa - 1015.48, Europe - 723.06, NortH America - 539.79, SoutH America 396.58, Oceania - 34.96 |
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