GAZAR

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SELECT from WORLD Tutorial sqlzoo

SELECT from WORLD Tutorial sqlzoo

Let's practice some SQL commands for SELECT together:

SQLZoo is an invaluable resource for individuals seeking to sharpen their SQL skills through interactive tutorials and exercises. Established as an online platform, SQLZoo offers a comprehensive range of SQL challenges, from basic queries to advanced database manipulation tasks.

Observe the result of running this SQL command to show the name, continent and population of all countries.

SELECT name, continent, population FROM world

Show the name for the countries that have a population of at least 200 million. 200 million is 200000000, there are eight zeros.

SELECT name 
FROM world
WHERE population > 200000000

Give the name and the per capita GDP for those countries with a population of at least 200 million.

SELECT name,gdp/population 
FROM world
WHERE population > 200000000

Show the name and population in millions for the countries of the continent 'South America'. Divide the population by 1000000 to get population in millions.

SELECT name, population/1000000 
FROM world
WHERE continent='South America'

Show the name and population for France, Germany, Italy

SELECT name, population From world
WHERE name IN("France","Germany","Italy")

Show the countries which have a name that includes the word 'United'

SELECT name FROM world
WHERE name LIKE "%United%"

Two ways to be big: A country is big if it has an area of more than 3 million sq km or it has a population of more than 250 million.

Show the countries that are big by area or big by population. Show name, population and area.

SELECT name,population,area FROM world
WHERE population > 250000000 OR area > 3000000

Exclusive OR (XOR). Show the countries that are big by area (more than 3 million) or big by population (more than 250 million) but not both. Show name, population and area.

  • Australia has a big area but a small population, it should be included.
  • Indonesia has a big population but a small area, it should be included.
  • China has a big population and big area, it should be excluded.
  • United Kingdom has a small population and a small area, it should be excluded.
SELECT name,population,area
FROM world
WHERE (population > 250000000 AND area < 3000000) OR (population < 250000000 AND area > 3000000)

Show the name and population in millions and the GDP in billions for the countries of the continent 'South America'. Use the ROUND function to show the values to two decimal places.

For Americas show population in millions and GDP in billions both to 2 decimal places.

  • Millions and billions
  • Missing decimals
SELECT name, ROUND(population/1000000.0,2), ROUND(gdp/1000000000.0,2) FROM world
WHERE continent='South America'

Show the name and per-capita GDP for those countries with a GDP of at least one trillion (1000000000000; that is 12 zeros). Round this value to the nearest 1000.

Show per-capita GDP for the trillion dollar countries to the nearest $1000.

SELECT name, ROUND(gdp/population,-3) FROM world
where GDP > 1000000000000

Greece has capital Athens.

Each of the strings 'Greece', and 'Athens' has 6 characters.

Show the name and capital where the name and the capital have the same number of characters.

You can use the LENGTH function to find the number of characters in a string

SELECT name, capital
FROM world
WHERE LENGTH(name) = LENGTH(capital)

The capital of Sweden is Stockholm. Both words start with the letter 'S'.

Show the name and the capital where the first letters of each match. Don't include countries where the name and the capital are the same word.

  • You can use the function LEFT to isolate the first character.
  • You can use <> as the NOT EQUALS operator.
SELECT name, capital
FROM world
WHERE LEFT(name,1) = LEFT(capital,1) && name <> capital

Equatorial Guinea and Dominican Republic have all of the vowels (a e i o u) in the name. They don't count because they have more than one word in the name.

Find the country that has all the vowels and no spaces in its name.

  • You can use the phrase name NOT LIKE '%a%' to exclude characters from your results.
  • The query shown misses countries like Bahamas and Belarus because they contain at least one 'a'
SELECT name
   FROM world
WHERE name LIKE '%a%'
AND name LIKE '%e%'
AND name LIKE '%i%'
AND name LIKE '%o%'
AND name LIKE '%u%'
AND name NOT LIKE '% %'

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