sqlzoo练习题答，已更完。
SELECT basics
1、The example uses a WHERE clause to show the population of ‘France’. Note that strings (pieces of text that are data) should be in ‘single quotes’;
Modify it to show the population of Germany
SELECT population FROM world WHERE name = 'Germany'
2、Checking a list The word IN allows us to check if an item is in a list. The example shows thename and population for the countries ‘Brazil’, ‘Russia’, ‘India’ and ‘China’.
Show the name and the population for ‘Sweden’, ‘Norway’ and ‘Denmark’.
SELECT name, population FROM world WHERE name IN ('Sweden', 'Norway', 'Denmark');
3、Which countries are not too small and not too big? BETWEEN allows range checking (range specified is inclusive of boundary values). The example below shows countries with an area of 250,000-300,000 sq. km. Modify it to show the country and the area for countries with an area between 200,000 and 250,000.
SELECT name, area FROM world WHERE area BETWEEN 200000 AND 250000
SELECT from WORLD
1、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;
2、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 >= 200000000;
3、Give the name and the per capita GDP for those countries with a population of at least 200 million
HELP:How to calculate per capita GDP
per capita GDP is the GDP divided by the population GDP/population
select name, gdp/population from world where population >= 200000000;
4、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';
5、Show the name and population for France, Germany, Italy
select name, population from world where name IN('France','Germany','Italy');
6、Show the countries which have a name that includes the word ‘United’
select name from world where name like '%United%';
7、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;
8、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 (area >= 3000000 and population <= 250000000) or (area <= 3000000 and population >= 250000000);
9、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 both to 2 decimal places.
Millions and billions
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';
10、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;
或
select name,round(GDP/population/1000,0)*1000 from world where gdp>=1000000000000
11、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,capital FROM world WHERE LENGTH(name) = LENGTH(capital)
12、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, capital FROM world WHERE LEFT(name,1) = LEFT(capital,1) AND name <> capital
13、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 '%a%' AND name LIKE '%e%' AND name LIKE '%i%' AND name LIKE '%o%' AND name LIKE '%u%') AND name not like '% %'
SELECT from Nobel
- Change the query shown so that it displays Nobel prizes for 1950.
SELECT yr, subject, winner FROM nobel WHERE yr = 1950
- Show who won the 1962 prize for Literature.
SELECT winner FROM nobel WHERE yr = 1962 AND subject = 'Literature'
- Show the year and subject that won ‘Albert Einstein’ his prize.
SELECT yr, subject FROM nobel WHERE winner = 'Albert Einstein'
- Give the name of the ‘Peace’ winners since the year 2000, including 2000.
SELECT winner FROM nobel WHERE yr >= 2000 AND subject = 'Peace'
- Show all details (yr, subject, winner) of the Literature prize winners for 1980 to 1989 inclusive.
SELECT * FROM nobel WHERE subject = 'Literature' AND yr BETWEEN 1980 AND 1989
6、Show all details of the presidential winners:
Theodore Roosevelt
Woodrow Wilson
Jimmy Carter
Barack Obama
SELECT * FROM nobel WHERE winner IN ('Theodore Roosevelt', 'Woodrow Wilson', 'Jimmy Carter', 'Barack Obama')
- Show the winners with first name John
SELECT winner FROM nobel WHERE winner LIKE 'John%'
- Show the year, subject, and name of Physics winners for 1980 together with the Chemistry winners for 1984.
SELECT * FROM nobel WHERE (subject = 'Physics' AND yr = 1980) OR (subject = 'Chemistry' AND yr = 1984)
- Show the year, subject, and name of winners for 1980 excluding(不包括) Chemistry and Medicine
SELECT * FROM nobel WHERE yr = 1980 AND subject NOT IN ('Chemistry', 'Medicine')
10、Show year, subject, and name of people who won a ‘Medicine’ prize in an early year (before 1910, not including 1910) together with winners of a ‘Literature’ prize in a later year (after 2004, including 2004)
SELECT * FROM nobel WHERE (subject = 'Medicine' AND yr < 1910) OR (subject = 'Literature' AND yr >= 2004)
11、Find all details of the prize won by PETER GRÜNBERG
Non-ASCII characters
The u in his name has an umlaut. You may find this link useful
https://en.wikipedia.org/wiki/%C3%9C#Keyboarding
SELECT * FROM nobel WHERE winner = 'PETER GRÜNBERG'
12、Find all details of the prize won by EUGENE O’NEILL
Escaping single quotes
You can’t put a single quote in a quote string directly. You can use two single quotes within a quoted string.
SELECT * FROM nobel WHERE winner = 'EUGENE O''NEILL'
- Knights in order
List the winners, year and subject where the winner starts with Sir. Show the the most recent first, then by name order.
SELECT winner, yr, subject FROM nobel WHERE winner LIKE 'Sir%' ORDER BY yr DESC , winner
14、The expression subject IN (‘Chemistry’,‘Physics’) can be used as a value - it will be 0 or 1.
Show the 1984 winners and subject ordered by subject and winner name; but list Chemistry and Physics last.
SELECT winner, subject FROM nobel WHERE yr=1984 ORDER BY subject IN ('Chemistry','Physics'),subject,winner
或
SELECT winner, subject FROM nobel WHERE yr='1984' ORDER BY CASE WHEN subject IN ('physics','chemistry') THEN 1 ELSE 0 END, subject,winner
注：若这两种方式执行不出笑脸，右上角设置，选择MySQL。
SELECT within SELECT
- List each country name where the population is larger than that of ‘Russia’.
SELECT name FROM world WHERE population > (SELECT population FROM world WHERE name='Russia')
- Show the countries in Europe with a per capita GDP greater than ‘United Kingdom’.
Per Capita GDP
The per capita GDP is the gdp/population
select name from world where continent = 'Europe' and gdp/population > ( select gdp/population from world where name = 'United Kingdom' )
- List the name and continent of countries in the continents containing either Argentina or Australia. Order by name of the country.
select name, continent from world where continent in (select continent from world where name = 'Australia' or name = 'Argentina') order by name
- Which country has a population that is more than Canada but less than Poland? Show the name and the population.
select name, population from world where population > (select population from world where name = 'Canada') and population < (select population from world where name = 'Poland')
5、Germany (population 80 million) has the largest population of the countries in Europe. Austria (population 8.5 million) has 11% of the population of Germany.
Show the name and the population of each country in Europe. Show the population as a percentage of the population of Germany.
select name, concat(round( population/(select population from world where name = 'Germany')*100),'%') as percentage from world where continent = 'Europe';
- Which countries have a GDP greater than every country in Europe? [Give the name only.] (Some countries may have NULL gdp values)
select name from world where gdp > all(select gdp from world where gdp > 0 and continent = 'Europe')
- Find the largest country (by area) in each continent, show the continent, the name and the area:
SELECT continent, name, area FROM world x WHERE area >= ALL (SELECT area FROM world y WHERE y.continent=x.continent AND area>0)
- List each continent and the name of the country that comes first alphabetically.
select continent, name from world a where name = (select min(name) from world b where a.continent = b.continent)
9、Find the continents where all countries have a population <= 25000000. Then find the names of the countries associated with these continents. Show name, continent and population.
select name, continent, population from world a where 25000000 >=all (select population from world b where a.continent = b.continent)
10、Some countries have populations more than three times that of all of their neighbours (in the same continent). Give the countries and continents.
select name, continent from world a where population/3 >= all(select population from world b where a.continent = b.continent and a.name <> b.name)
