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-- 1. What are the names of countries with population greater than 8 million? | |
SELECT Name | |
FROM country | |
WHERE Population > 8000000; | |
-- 2. What are the names of countries that have “land” in their names? | |
SELECT name | |
FROM country | |
WHERE name LIKE '%land%'; | |
-- 3. What are the names of the cities with population in between 500,000 and 1 million? | |
SELECT name | |
FROM city | |
WHERE population >= 500000 and population <= 1000000; | |
-- 4. What's the name of all the countries on the continent ‘Europe’? | |
SELECT name | |
FROM country | |
WHERE continent = 'Europe'; | |
-- 5. What are the names of all the cities in the Netherlands? | |
SELECT name | |
FROM city | |
WHERE countryCode = 'NLD'; | |
-- 6. What is the population of Rotterdam? | |
SELECT population | |
FROM city | |
WHERE name = 'Rotterdam'; | |
-- 7. Which countries don't have a head of state? Hint: looks for NULL and '' values | |
SELECT name | |
FROM country | |
WHERE HeadOfState is null or HeadOfState = ''; | |
-- 8. What's the top 10 least populated cities? Return the name and population | |
SELECT name, population | |
FROM city | |
ORDER BY population asc | |
limit 10; | |
-- 9. What countries in Africa have the local name the same as their common name? | |
SELECT name | |
FROM country | |
WHERE LocalName = name and Continent = 'Africa'; | |
-- 10. What countries have Spanish as official language? Hint: see countrylanguage table | |
SELECT country.name | |
FROM country | |
JOIN countrylanguage on country.Code = countrylanguage.CountryCode | |
WHERE countrylanguage.`Language` = 'Spanish' AND countrylanguage.IsOfficial = 'T'; | |
-- 11. What countries have official languages spoken between 1% and 10% of the population? | |
SELECT country.name | |
FROM country | |
JOIN countrylanguage on country.Code = countrylanguage.CountryCode | |
WHERE countrylanguage.IsOfficial = 'T' and countrylanguage.Percentage >= 1 and countrylanguage.Percentage <= 10; | |
-- 12. What languages are spoken by over 90% of the population of a country? Return just the language names, but don't repeat entries | |
SELECT DISTINCT language | |
FROM countrylanguage | |
WHERE Percentage > 90; | |
-- 13. In which countries is 'Creole English' used? Order by descending percentage of speakers | |
SELECT country.name | |
FROM country | |
JOIN countrylanguage on country.Code = countrylanguage.CountryCode | |
WHERE countrylanguage.`Language` = 'Creole English' | |
ORDER BY countrylanguage.Percentage DESC; | |
-- 14. What are the 5 oldest countries (by independence date) with some form of republic government? Tip: there are multiple types of republic | |
SELECT name | |
FROM country | |
WHERE GovernmentForm LIKE '%Republic%' | |
ORDER BY IndepYear ASC LIMIT 5; | |
-- 15. For each country, how many people speak each language? Important: we want absolute values, not a percentage. Return the name of the country, the name of the language, and number of speakers of that language - Hint: you need both the country and countrylanguage tables - Hint: you can do calculations between columns, for example (SELECT a - b from table;) | |
SELECT country.name, countrylanguage.`Language`, (countrylanguage.Percentage / 100 * country.Population) as 'Number of Speakers' | |
FROM country | |
JOIN countrylanguage on country.Code = countrylanguage.CountryCode; | |
-- BONUS | |
-- 1. What is the total population of the world? | |
SELECT SUM(population) as `World's Total Population` | |
FROM country; | |
-- 2. What is the average population of countries in Europe? | |
SELECT AVG(population) as `Europe's Average Population` | |
FROM country | |
WHERE Continent = 'Europe'; | |
-- 3. How many *official* languages are spoken in Belgium (`BEL`)? Return the country code, and the number of languages as "Number of Languages" | |
SELECT countryCode, COUNT(language) as 'Number of Languages' | |
FROM countrylanguage | |
WHERE IsOfficial = 'T' and CountryCode = 'BEL'; |
Thank you for the feedback. Working on it.
Updated ✅
Very good, for question 11, you could also use the BETWEEN operator, but your query works, well done!
Thank you so much. I'll keep the advice in mind.
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Question 10: The
IsOfficial
field typically uses 'T' for true, nottrue
.Question 11: The percentage should include 1% and 10%, and
IsOfficial
should be 'T'.Question 15: The calculation is missing something, can you see what?
Qustion 3 (Bonus): The
IsOfficial
field should be 'T'.