Difference between revisions of "SUM and COUNT"
Line 1: | Line 1: | ||
<h3>BBC Country Profile: Aggregate functions</h3> | <h3>BBC Country Profile: Aggregate functions</h3> | ||
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. | 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. | ||
+ | <div class='ref_section'> | ||
+ | <table class='db_ref'> | ||
+ | <caption>bbc</caption> | ||
+ | <tr> | ||
+ | <th>name</th> | ||
+ | <th>region</th> | ||
+ | <th>area</th> | ||
+ | <th>population</th> | ||
+ | <th>gdp</th> | ||
+ | </tr> | ||
+ | <tr> | ||
+ | <td>Afghanistan</td> | ||
+ | <td>South Asia</td> | ||
+ | <td align='right'>652225</td> | ||
+ | <td align='right'>26000000</td> | ||
+ | <td></td> | ||
+ | </tr> | ||
+ | <tr> | ||
+ | <td>Albania</td> | ||
+ | <td>Europe</td> | ||
+ | <td align='right'>28728</td> | ||
+ | <td align='right'>3200000</td> | ||
+ | <td align='right'>6656000000</td> | ||
+ | </tr> | ||
+ | <tr> | ||
+ | <td>Algeria</td> | ||
+ | <td>Middle East</td> | ||
+ | <td align='right'>2400000</td> | ||
+ | <td align='right'>32900000</td> | ||
+ | <td align='right'>75012000000</td> | ||
+ | </tr> | ||
+ | <tr> | ||
+ | <td>Andorra</td> | ||
+ | <td>Europe</td> | ||
+ | <td align='right'>468</td> | ||
+ | <td align='right'>64000</td> | ||
+ | <td></td> | ||
+ | </tr> | ||
+ | <tr> | ||
+ | <td colspan='5'>...</td> | ||
+ | </tr> | ||
+ | </table> | ||
+ | </div> | ||
<h2>Exercises</h2> | <h2>Exercises</h2> |
Revision as of 08:45, 6 August 2012
BBC 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.
name | region | area | population | gdp |
---|---|---|---|---|
Afghanistan | South Asia | 652225 | 26000000 | |
Albania | Europe | 28728 | 3200000 | 6656000000 |
Algeria | Middle East | 2400000 | 32900000 | 75012000000 |
Andorra | Europe | 468 | 64000 | |
... |
Exercises
Using SUM, Count, MAX, DISTINCT and ORDER BY.
Show the total population of the world.
bbc(name, region, area, population, gdp)
SELECT SUM(population)
FROM bbc
SELECT SUM(population)
FROM bbc
List all the regions - just once each.
SELECT DISTINCT(region)
FROM bbc
Give the total GDP of Africa
SELECT SUM(gdp)
FROM bbc
WHERE region = 'Africa'
How many countries have an area of at least 1000000
SELECT COUNT(name)
FROM bbc
WHERE area >= 1000000
What is the total population of ('France','Germany','Spain')
SELECT SUM(population)
FROM bbc
WHERE name IN('France','Germany','Spain')
For each region show the region and number of countries.
SELECT region, COUNT(name)
FROM bbc
GROUP BY(region)
For each region show the region and number of countries with populations of at least 10 million.
SELECT region, COUNT(name)
FROM bbc
WHERE population >= 10000000
GROUP BY(region)
List the regions with total populations of at least 100 million.
SELECT region
FROM bbc
GROUP BY region
HAVING SUM(population)>= 100000000
The nobel table can be used to practice more SUM and COUNT functions.