text: -- SQL tasks from https://sqlzoo.net/wiki/SQL_Tutorial
  
  /*
  ===============================================================
  **                                                           **
    ***** *****  TUTORIAL - 1 - SELECT from world  ***** *****    
  **                                                           **
  ===============================================================
  */
  
  -- 1- Observe the result of running this SQL command to show the name, continent and population of all countries.
  
  SELECT name, continent, population FROM world
  
  -- 2- 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
  
  -- 3- 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
  
  -- 4- Show the name and population in millions for the countries of the continent 'South America'. 
  
  SELECT name, population/1000000
  FROM world
  WHERE continent = 'South America'
  
  -- 5- Show the name and population for France, Germany, Italy
  
  SELECT name, population FROM world
  where name in ('France','Germany', 'Italy');
  
  -- 6- Show the countries which have a name that includes the word 'United'
  
  SELECT name
  FROM world
  WHERE name LIKE '%united%'
  
  -- 7- Show the countries that are big by area or big by population. Show name, population and area.
  
  SELECT name, population, area FROM world where area > 3000000 or population > 250000000
  
  -- 8- 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.
  
  SELECT name, population, area
  FROM world
  WHERE (area < 3000000 AND population > 250000000) OR (area > 3000000 AND population < 250000000)
  
  -- 9- Show the name and population in millions and the GDP in billions for the countries of the continent 'South America'.
  
  SELECT name,ROUND(population/1000000,2), ROUND(gdp/1000000000,2)
  FROM world
  WHERE continent = 'South America'
  
  -- 10- 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
  
  SELECT name, ROUND(gdp/population,-3)
  FROM world
  WHERE gdp > 1000000000000
  
  -- 11- Show the name and capital where the name and the capital have the same number of characters.
  
  SELECT name, capital
  FROM world
  WHERE LEN(name) = LEN(capital)
  
  -- 12- 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.
  
  SELECT name, capital
  FROM world
  WHERE (LEFT(name, 1) = LEFT(capital, 1)) AND (name <> capital)
  
  -- 13- Find the country that has all the vowels and no spaces in its name.
  
  SELECT name
  FROM world
  WHERE name LIKE '%e%' AND 
        name LIKE '%i%' AND
        name LIKE '%o%' AND
        name LIKE '%u%' AND
        name NOT LIKE '% %'