# Difference between revisions of "SQLZOO:SELECT from WORLD Tutorial/zh"

 語言: [[:{{#invoke:String|sub|SQLZOO:SELECT from WORLD Tutorial/zh ``` |1 |Expression error: Unrecognized punctuation character "{". ``` }}|English]]
namecontinentarea populationgdp
AfghanistanAsia6522302550010020343000000
AlbaniaEurope28748 2831741 12960000000
AlgeriaAfrica2381741 37100000 188681000000
AndorraEurope46878115 3712000000
AngolaAfrica1246700 20609294 100990000000
...

name:國家名稱
continent:洲份
area:面積
population:人口
gdp:國內生產總值

## Country Profile

```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
```

USA, India, and China are big in population and big by area. Exclude these countries.

Show the countries that are big by area or big by population but not both. Show name, population and area.

```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.

For South America show population in millions and GDP in billions to 2 decimal places.
Divide by 1000000 (6 zeros) for millions. Divide by 1000000000 (9 zeros) for billions.
```SELECT name, ROUND(population/1000000,2),
ROUND(gdp/1000000000,2)
FROM world
WHERE continent='South America'
```

Show the 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.

Show the name - but substitute Australasia for Oceania - for countries beginning with N.
```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%'
```
Show the name and the continent - but substitute Eurasia for Europe and Asia; substitute America - for each country in North America or South America or Caribbean. Show countries beginning with A or B
```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
Show the name, the original continent and the new continent of all countries.
```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
ORDER BY name
```