Difference between revisions of "SUM and COUNT"
From SQLZOO
| (6 intermediate revisions by 2 users not shown) | |||
| 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> | ||
<p>[[Using SUM, Count, MAX, DISTINCT and ORDER BY]].</p> | <p>[[Using SUM, Count, MAX, DISTINCT and ORDER BY]].</p> | ||
| − | <div class="summary">Summary</div> | + | <div class="progress_panel"><div> |
| − | + | <div class="summary">Summary</div> | |
| − | <div class="progressbarbg"> | + | <div class="progressbarbg"> |
| − | + | <div class="progressbar"></div> | |
| − | </div> | + | </div> |
| + | </div></div> | ||
<div class='qu'> | <div class='qu'> | ||
| − | Show the total '''population''' of the world. | + | Show the total '''population''' of the world. |
| + | |||
| + | |||
bbc('''name''', '''region''', '''area''', '''population''', '''gdp''') | bbc('''name''', '''region''', '''area''', '''population''', '''gdp''') | ||
<source lang='sql' class='def'> | <source lang='sql' class='def'> | ||
| Line 54: | Line 100: | ||
<source lang='sql' class='ans'> | <source lang='sql' class='ans'> | ||
| − | SELECT COUNT( | + | SELECT COUNT(name) |
FROM bbc | FROM bbc | ||
WHERE area >= 1000000 | WHERE area >= 1000000 | ||
| Line 113: | Line 159: | ||
<div class="lsclear">Clear your results</div> | <div class="lsclear">Clear your results</div> | ||
| − | < | + | <p><div class="quizlink">[[SUM and COUNT Quiz]]</div></p> |
| − | + | ||
<p>[[The nobel table can be used to practice more SUM and COUNT functions.]]</p> | <p>[[The nobel table can be used to practice more SUM and COUNT functions.]]</p> | ||
<p>[[The_JOIN_operation |The next tutorial is looks at the Table Tennis database. It shows how queries may use records from two related tables.]] | <p>[[The_JOIN_operation |The next tutorial is looks at the Table Tennis database. It shows how queries may use records from two related tables.]] | ||
Revision as of 11:54, 15 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.
Summary
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
Clear your results
The nobel table can be used to practice more SUM and COUNT functions.
