Difference between revisions of "SQLZOO:SELECT basics"
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| − | = | + | <div class="ref_section"> |
| − | + | <table class='db_ref'> | |
| − | <table | + | <tr><th>name</th><th>region</th><th>area</th> |
| − | <th>name</th> | + | <th>population</th><th>gdp</th></tr> |
| − | <th>region</th> | + | <tr><td>Afghanistan</td><td>South Asia</td><td class="r">652225</td><td class="r">26000000</td><td class="r"></td></tr> |
| − | <th>area</th> | + | <tr><td>Albania</td><td>Europe</td><td class="r">28728</td><td class="r">3200000</td><td class="r">6656000000</td></tr> |
| − | <th>population</th> | + | <tr><td>Algeria</td><td>Middle East</td><td class="r">2400000</td><td class="r">32900000</td><td class="r">75012000000</td></tr> |
| − | <th>gdp</th> | + | <tr><td>Andorra</td><td>Europe</td><td class="r">468</td><td class="r">64000</td><td class="r"></td></tr><tr> |
| − | </tr> | + | <td>Angola</td><td>Africa</td><td class="r">1250000</td><td class="r">14500000</td><td class="r">14935000000</td></tr> |
| − | <tr> | + | |
| − | <td>Afghanistan</td> | + | |
| − | <td>South Asia</td> | + | |
| − | <td | + | |
| − | <td | + | |
| − | <td></td> | + | |
| − | </tr> | + | |
| − | <tr> | + | |
| − | <td>Albania</td> | + | |
| − | <td>Europe</td> | + | |
| − | <td | + | |
| − | <td | + | |
| − | <td | + | |
| − | </tr> | + | |
| − | <tr> | + | |
| − | <td>Algeria</td> | + | |
| − | <td>Middle East</td> | + | |
| − | <td | + | |
| − | <td | + | |
| − | <td | + | |
| − | </tr> | + | |
| − | <tr> | + | |
| − | <td>Andorra</td> | + | |
| − | <td>Europe</td> | + | |
| − | <td | + | |
| − | <td | + | |
| − | <td></td> | + | |
| − | </tr> | + | |
<tr> | <tr> | ||
<td colspan='5'>...</td> | <td colspan='5'>...</td> | ||
</tr> | </tr> | ||
</table> | </table> | ||
| + | </div> | ||
| + | |||
| + | ==Introducing the BBC Table of Countries== | ||
| + | <p>This tutorial introduces SQL as a query language. We will be using the SELECT command on the table '''bbc''':</p> | ||
| + | |||
| + | <div class="progress_panel"><div> | ||
| + | <div class="summary">Summary</div> | ||
| + | <div class="progressbarbg"> | ||
| + | <div class="progressbar"></div> | ||
| + | </div> | ||
| + | </div></div> | ||
| + | <div class='extra_space' style='width:1em; height:6em;'></div> | ||
| + | |||
<div class='qu'> | <div class='qu'> | ||
The example shows the population of 'France'. | The example shows the population of 'France'. | ||
| Line 58: | Line 43: | ||
</div> | </div> | ||
| + | ==Per Capita GDP== | ||
<div class='qu'> | <div class='qu'> | ||
<div>This query shows the population density <code>population/area</code> | <div>This query shows the population density <code>population/area</code> | ||
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</div> | </div> | ||
| + | ==Small and wealthy== | ||
<div class='qu'> | <div class='qu'> | ||
Where to find some very small, very rich countries.<br/> | Where to find some very small, very rich countries.<br/> | ||
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</div> | </div> | ||
| − | + | ==Scandinavia== | |
<div class='qu'> | <div class='qu'> | ||
Checking a list The word <b>IN</b> allows us to check if an item is in a list. | Checking a list The word <b>IN</b> allows us to check if an item is in a list. | ||
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</div> | </div> | ||
| + | ==Starts with G== | ||
<div class='qu'> | <div class='qu'> | ||
What are the countries beginning with G? | What are the countries beginning with G? | ||
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</div> | </div> | ||
| + | ==Just the right size== | ||
<div class='qu'> | <div class='qu'> | ||
Which countries are not too small and not too big? | Which countries are not too small and not too big? | ||
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</source> | </source> | ||
</div> | </div> | ||
| + | |||
| + | <div> | ||
| + | <div class="lsclear">Clear your results</div> | ||
| + | <p><div class="quizlink">[[SELECT Quiz]]</div></p> | ||
| + | </div> | ||
| + | <p>You are ready for tutorial one:[[SELECT_from_BBC_Tutorial |SELECT statements with WHERE.]]</p> | ||
| + | |||
| + | |||
| + | {{Languages}} | ||
Revision as of 16:50, 28 October 2012
| 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 | |
| Angola | Africa | 1250000 | 14500000 | 14935000000 |
| ... | ||||
Contents |
Introducing the BBC Table of Countries
This tutorial introduces SQL as a query language. We will be using the SELECT command on the table bbc:
Summary
The example shows the population of 'France'. Strings should be in 'single quotes';
Show the population of Germany
SELECT population FROM bbc WHERE name = 'France'
SELECT population FROM bbc WHERE name = 'Germany'
Per Capita GDP
This query shows the population density
population/area
for each country where the area is over 5,000,000 km2.Show the per capita gdp:
gdp/population
for each country where the area is over 5,000,000 km2SELECT name, population/area FROM bbc WHERE area > 5000000
SELECT name, gdp/population FROM bbc WHERE area > 5000000
Small and wealthy
Where to find some very small, very rich countries.
We use AND to ensure that two or more conditions hold
true.
The example shows the countries where the population is small and the
gdp is high.
Show the name and region where the area is less then 2000 and the gdp is more than 5000000000
SELECT name , region FROM bbc WHERE population < 2000000 AND gdp > 5000000000
SELECT name , region FROM bbc WHERE area < 2000 AND gdp > 5000000000
Checking a list The word IN allows us to check if an item is in a list. The example shows the name and population for the countries 'Ireland', 'Iceland' and 'Denmark'
Show the name and the population for 'Denmark', 'Finland', 'Norway', 'Sweden'
SELECT name, population FROM bbc WHERE name IN ('Ireland', 'Iceland', 'Denmark')
SELECT name, population FROM bbc WHERE name IN ('Denmark', 'Finland', 'Norway', 'Sweden')
Starts with G
What are the countries beginning with G?
The word LIKE permits pattern matching - % is the wildcard.
The examples shows countries beginning with D
Show each country that begins with G
SELECT name FROM bbc WHERE name LIKE 'D%'
SELECT name FROM bbc WHERE name LIKE 'G%'
Just the right size
Which countries are not too small and not too big?
BETWEEN allows range checking - note that it is inclusive.
Show the area in 1000 square km. Show area/1000 instead of area
SELECT name, area FROM bbc WHERE area BETWEEN 207600 AND 244820
SELECT name, area/1000 FROM bbc WHERE area BETWEEN 207600 AND 244820
Clear your results
You are ready for tutorial one:SELECT statements with WHERE.
| Language: | English |
|---|
