Difference between revisions of "SELECT from WORLD Tutorial"
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Revision as of 17:53, 1 December 2019
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In this tutorial you will use the SELECT command on the table
- 1 Introduction
- 2 Large Countries
- 3 Per capita GDP
- 4 South America In millions
- 5 France, Germany, Italy
- 6 United
- 7 Two ways to be big
- 8 One or the other (but not both)
- 9 Rounding
- 10 Trillion dollar economies
- 11 Name and capital have the same length
- 12 Matching name and capital
- 13 All the vowels
- 14 What Next
Read the notes about this table. Observe the result of running this SQL command to show the name, continent and population of all countries.
SELECT name, continent, population FROM world
SELECT name, continent, population FROM world
How to use WHERE to filter records. 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 = 64105700
SELECT name FROM world WHERE population>200000000
Per capita GDP
name and the per capita GDP for those countries with a
population of at least 200 million.
per capita GDP is the GDP divided by the population GDP/population
SELECT name, gdp/population FROM world WHERE population > 200000000
South America In millions
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'
France, Germany, Italy
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
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 area>3000000 or population>250000000
One or the other (but not both)
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 or area>3000000) and not(population>250000000 and area>3000000)
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.
SELECT name, ROUND(population/1000000,2), ROUND(gdp/1000000000,2) FROM world WHERE continent='South America'
Trillion dollar economies
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
Name and capital have the same length
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, LENGTH(name), continent, LENGTH(continent), capital, LENGTH(capital) FROM world WHERE name LIKE 'G%'
SELECT name, capital FROM world WHERE LENGTH(name)=LENGTH(capital)
Matching name and capital
The capital of Sweden is Stockholm. Both words start with the letter 'S'.
- You can use the function LEFT to isolate the first character.
- You can use
<>as the NOT EQUALS operator.
SELECT name, LEFT(name,1), capital FROM world
SELECT name,capital FROM world WHERE LEFT(name,1)=LEFT(capital,1) AND name<>capital
All the vowels
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 'B%' AND name NOT LIKE '%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 '% %'
- BBC QUIZ
- You can to continue practising the the same techniques
and gain more experience of the basic skills on the Nobel table.
WHEREstatement using the
- You can learn about nested statements, these are instructive and entertaining, but not essential for beginners.
SELECTstatements using the