Difference between revisions of "SELECT from WORLD Tutorial"
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<li>Caribbean islands starting with 'B' go to '''North America''', other Caribbean islands go to '''South America'''</li> | <li>Caribbean islands starting with 'B' go to '''North America''', other Caribbean islands go to '''South America'''</li> | ||
<li>Order by country name in ascending order</li> | <li>Order by country name in ascending order</li> | ||
+ | <li>Test your query using the WHERE clause with the following:</li> | ||
+ | <source lang='sql'>WHERE tld IN ('.ag','.ba','.bb','.ca','.cn','.nz','.ru','.tr','.uk')</source> | ||
</ul> | </ul> | ||
<div class=imper>Show the name, the original continent and the new continent of all countries.</div> | <div class=imper>Show the name, the original continent and the new continent of all countries.</div> | ||
<source lang='sql' class='def'> | <source lang='sql' class='def'> | ||
+ | SELECT name, continent,tld | ||
+ | FROM world | ||
+ | WHERE tld IN ('.ag','.ba','.bb','.ca','.cn','.nz','.ru','.tr','.uk') | ||
</source> | </source> | ||
<source lang='sql' class='ans'> | <source lang='sql' class='ans'> | ||
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ELSE continent END | ELSE continent END | ||
FROM world | FROM world | ||
− | + | WHERE tld IN ('.ag','.ba','.bb','.ca','.cn','.nz','.ru','.tr','.uk')</source> | |
</div> | </div> | ||
Revision as of 16:25, 16 September 2016
Language: | English • 日本語 • 中文 |
---|
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 |
... |
Country Profile
In this tutorial you will use the SELECT command on the table world
:
Read the notes about this table. Observe the result of running a simple SQL command.
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>250000000
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.
per capita GDP is the GDP divided by the population GDP/population
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 area>3000000
or population>250000000
Exclusive OR (XOR). Show the countries that are big by area or big by population 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)
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.
SELECT name, ROUND(population/1000000,2),
ROUND(gdp/1000000000,2)
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
Harder Questions
The CASE statement shown is used to substitute North America for Caribbean in the third column.
SELECT name, continent,
CASE WHEN continent='Caribbean' THEN 'North America'
ELSE continent END
FROM world
WHERE name LIKE 'J%'
SELECT name, CASE WHEN continent='Oceania' THEN 'Australasia'
ELSE continent END
FROM world
WHERE name LIKE 'N%'
SELECT name, CASE WHEN continent IN ('Europe','Asia') THEN 'Eurasia'
WHEN continent IN ('North America','South America','Caribbean') THEN 'America'
ELSE continent END
FROM world
WHERE name BETWEEN 'A' AND 'C'
Put the continents right...
- Oceania becomes Australasia
- Countries in Eurasia and Turkey go to Europe/Asia
- Caribbean islands starting with 'B' go to North America, other Caribbean islands go to South America
- Order by country name in ascending order
- Test your query using the WHERE clause with the following:
WHERE tld IN ('.ag','.ba','.bb','.ca','.cn','.nz','.ru','.tr','.uk')
SELECT name, continent,tld
FROM world
WHERE tld IN ('.ag','.ba','.bb','.ca','.cn','.nz','.ru','.tr','.uk')
SELECT name,continent,
CASE WHEN continent = 'Eurasia' OR name='Turkey' THEN 'Europe/Asia'
WHEN continent IN ('Oceania') THEN 'Australasia'
WHEN continent = 'Caribbean' AND name LIKE 'B%' THEN 'North America'
WHEN continent = 'Caribbean' THEN 'South America'
ELSE continent END
FROM world
WHERE tld IN ('.ag','.ba','.bb','.ca','.cn','.nz','.ru','.tr','.uk')
What Next
- BBC QUIZ
- You can play a game: Find the duplicate
- 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 thenobel
table. - You can learn about nested statements, these are instructive and entertaining, but not essential for beginners.
Nested
SELECT
statements using theworld
table.