查询表格:
表格说明:
Observe the result of running this SQL command to show the name, continent and population of all countries.
SELECT name, continent, population FROM world
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
Give the name and the per capita GDP for those countries with a population of at least 200 million.
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.
【知识点】异或
a XOR b
,只有当满足条件a或满足条件b,并且不能同时满足ab时,才会被判定为满足条件。
SELECT name, population, area
FROM world
WHERE area > 3000000 XOR population > 250000000
解法2:
SELECT name, population, area FROM world
WHERE (area > 3000000 AND population < 250000000) OR (area < 3000000 AND population > 250000000);
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.
【知识点】
ROUND()
ROUND(f,p)
returns f rounded to p decimal places. 如,ROUND(7253.86, 0)
-> 7254ROUND(7253.86, 1)
-> 7253.9ROUND(7253.86,-3)
-> 7000
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
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.
【知识点】
LENGTH()
LENGTH(s)
returns the number of characters in string s.
SELECT name, capital
FROM world
WHERE LENGTH(name) = LENGTH(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.
<>
as the NOT EQUALS operator.【知识点】
LEFT()
LEFT(s,n)
allows you to extract n characters from the start of the string s. 如,LEFT('Hello world', 4)
-> 'Hell'
SELECT name, capital
FROM world
WHERE LEFT(name,1) = LEFT(capital,1) AND name <> capital
Find the country that has all the vowels and no spaces in its name.
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 '% %'