SELECT from WORLD Tutorial

name	continent	area	population	gdp
Afghanistan	Asia	652230	25500100	20343000000
Albania	Europe	28748	2831741	12960000000
Algeria	Africa	2381741	37100000	188681000000
Andorra	Europe	468	78115	3712000000
Angola	Africa	1246700	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.

SELECT name, continent, population FROM world

SELECT name, continent, population FROM world

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.

SELECT name FROM world
WHERE population = 64105700

SELECT name FROM world
WHERE population>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

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

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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.

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

France, Germany, Italy

Show the name and population for France, Germany, Italy

SELECT name, population FROM world
  WHERE name IN ('France','Germany','Italy')

United

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)

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.

SELECT name, ROUND(population/1000000.0,2),
             ROUND(gdp/1000000000.0,2)
  FROM world
 WHERE continent='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.

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

For Microsoft SQL Server the function LENGTH is LEN

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'.

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, 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 '% %'

What Next

• BBC QUIZ
• You can to continue practising the the same techniques and gain more experience of the basic skills on the Nobel table. The WHERE statement using the nobel table.
• You can learn about nested statements, these are instructive and entertaining, but not essential for beginners. Nested SELECT statements using the world table.