SELECT from WORLD Tutorial

From SQLZoo
Language: Project:Language policy English  • 日本語  • 中文
namecontinentarea populationgdp
AfghanistanAsia6522302550010020343000000
AlbaniaEurope28748 2831741 12960000000
AlgeriaAfrica2381741 37100000 188681000000
AndorraEurope46878115 3712000000
AngolaAfrica1246700 20609294 100990000000
...


In this tutorial you will use the SELECT command on the table world:

Introduction

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

SELECTname,continent,populationFROMworld

SELECTname,continent,populationFROMworld

Large Countries

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. 

SELECTnameFROMworld
WHEREpopulation=64105700

SELECTnameFROMworld
WHEREpopulation>200000000

Per capita GDP

Give the 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 

SELECTname,gdp/populationFROMworld
WHEREpopulation>200000000

{{#ev:youtube|5Md75Wfpocs}}

South America In millions

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. 

SELECTname,population/1000000FROMworld
WHEREcontinent='South America'

France, Germany, Italy

Show the name and population for France, Germany, Italy 

SELECTname,populationFROMworld
WHEREnameIN('France','Germany','Italy')

United

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

SELECTnameFROMworld
WHEREnameLIKE'%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.

selectname,population,area
fromworld
wherearea>3000000
orpopulation>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.
selectname,population,area
fromworld
where
(population>250000000orarea>3000000)
andnot(population>250000000andarea>3000000)

Rounding

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.
Divide by 1000000 (6 zeros) for millions. Divide by 1000000000 (9 zeros) for billions.
For some version of SQL the division of an integer by an integer will be an integer. One way to prevent this is to divide by a floating point number such as 1000000.0.
SELECTname,ROUND(population/1000000.0,2),
ROUND(gdp/1000000000.0,2)
FROMworld
WHEREcontinent='South America'

Play the SELECT card game

SELECT Card Game

Trillion dollar economies

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ドル.

selectname,ROUND(gdp/population,-3)
fromworld
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

For Microsoft SQL Server the function LENGTH is LEN

SELECTname,LENGTH(name),continent,LENGTH(continent),capital,LENGTH(capital)
FROMworld
WHEREnameLIKE'G%'

SELECTname,capital
FROMworld
WHERELENGTH(name)=LENGTH(capital)

Matching name and 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.
SELECTname,LEFT(name,1),capital
FROMworld

SELECTname,capital
FROMworld
WHERELEFT(name,1)=LEFT(capital,1)
ANDname<>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'
SELECTname
FROMworld
WHEREnameLIKE'B%'
ANDnameNOTLIKE'%a%'

SELECTname
FROMworld
WHEREnameLIKE'%a%'
ANDnameLIKE'%e%'
ANDnameLIKE'%i%'
ANDnameLIKE'%o%'
ANDnameLIKE'%u%'
ANDnameNOTLIKE'% %'


What Next

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  • Served by: dill at 2026年01月10日T12:31