SQLZOO练习记录-SUM and COUNT

目录

SUM and COUNT

World Country Profile: Aggregate functions

SUM and COUNT Quiz

The nobel table can be used to practice more SUM and COUNT functions.

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SUM and COUNT

World Country Profile: Aggregate functions

1.Show the total population of the world.

SELECT SUM(population)
FROM world

2.List all the continents - just once each.

SELECT DISTINCT continent
FROM world

3.Give the total GDP of Africa

SELECT SUM(gdp)
FROM world
WHERE continent='Africa'

4.How many countries have an area of at least 1000000

SELECT COUNT(name)
FROM world
WHERE area>=1000000

5.What is the total population of ('Estonia', 'Latvia', 'Lithuania')

SELECT SUM(population)
FROM world
WHERE name IN ('Estonia','Latvia','Lithuania')

6.For each continent show the continent and number of countries.

SELECT continent, COUNT(name)
FROM world
GROUP BY continent

7.For each continent show the continent and number of countries with populations of at least 10 million.

SELECT continent, COUNT(name)
FROM world
WHERE population>=10000000
GROUP BY continent

8.List the continents that have a total population of at least 100 million.

SELECT continent
FROM world
GROUP BY continent
HAVING SUM(population)>=100000000

 

SUM and COUNT Quiz

1.C

2.A

3.D

4.E

5.B

6.E

7.D

8.D

 

The nobel table can be used to practice more SUM and COUNT functions.

1.Show the total number of prizes awarded.

SELECT COUNT(winner) 
FROM nobel

2.List each subject - just once

SELECT DISTINCT subject 
FROM nobel

3.Show the total number of prizes awarded for Physics.

SELECT COUNT(winner) 
FROM nobel
WHERE subject = 'Physics'

4.For each subject show the subject and the number of prizes.

SELECT subject, COUNT(winner) 
FROM nobel
GROUP BY subject

5.For each subject show the first year that the prize was awarded.

SELECT subject, MIN(yr) 
FROM nobel
GROUP BY subject

6.For each subject show the number of prizes awarded in the year 2000.

SELECT subject, COUNT(winner) 
FROM nobel
WHERE yr=2000
GROUP BY subject 

7.Show the number of different winners for each subject.

SELECT subject, COUNT(DISTINCT winner)
FROM nobel
GROUP BY subject

8.For each subject show how many years have had prizes awarded.

SELECT subject, COUNT(DISTINCT yr)
FROM nobel
GROUP BY subject

9.Show the years in which three prizes were given for Physics.

SELECT yr
FROM nobel
WHERE subject='Physics'
GROUP BY yr
HAVING COUNT(winner)=3 

10.Show winners who have won more than once.

SELECT winner
FROM nobel
GROUP BY winner
HAVING COUNT(*)>1

11.Show winners who have won more than one subject.

SELECT winner
FROM nobel
GROUP BY winner
HAVING COUNT(DISTINCT subject) >1

12.Show the year and subject where 3 prizes were given. Show only years 2000 onwards.

SELECT yr, subject
FROM nobel
WHERE yr>=2000
GROUP BY yr, subject 
HAVING COUNT(*)=3