SUM and COUNT

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World Country Profile: Aggregate functions

This tutorial is about aggregate functions such as COUNT, SUM and AVG. An aggregate function takes many values and delivers just one value. For example the function SUM would aggregate the values 2, 4 and 5 to deliver the single value 11.

namecontinentarea populationgdp
AfghanistanAsia6522302550010020343000000
AlbaniaEurope28748 2831741 12960000000
AlgeriaAfrica2381741 37100000 188681000000
AndorraEurope46878115 3712000000
AngolaAfrica1246700 20609294 100990000000
...

Exercises

Using SUM, Count, MAX, DISTINCT and ORDER BY.

Summary

Show the total population of the world.


world(name, continent, area, population, gdp)
SELECT SUM(population)
FROM world
SELECT SUM(population)
FROM world

List all the continents - just once each.

 
SELECT DISTINCT(continent)
FROM world

Give the total GDP of Africa

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

How many countries have an area of at least 1000000

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

What is the total population of ('France','Germany','Spain')

 
SELECT SUM(population)
FROM world
WHERE name IN('France','Germany','Spain')

Using GROUP BY and HAVING.

For each continent show the continent and number of countries.

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

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)

List the continents with total populations of at least 100 million.

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

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

The next tutorial looks at the Table Tennis database. It shows how queries may use records from two related tables.

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