Difference between revisions of "SELECT .. GROUP BY"

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<h1>SELECT .. GROUP BY</h1>
Host cities and continents for the Olympics Games are stored in the table <code>games</code>.
Notice that Europe appears in the table twice:
<caption align='center'>'''games'''</caption>
<tr><th align='center'>'''yr'''</th><th align='center'>'''city'''</th><th align='center'>'''continent'''</th></tr>
<tr><td>2000</td><td align='left'>Sydney</td><td align='left'>Australasia</td></tr>
<tr><td>2004</td><td align='left'>Athens</td><td align='left'>Europe</td></tr>
<tr><td>2008</td><td align='left'>Beijing</td><td align='left'>Asia</td></tr>
<tr><td>2012</td><td align='left'>London</td><td align='left'>Europe</td></tr>
<div class='ht'>
<div class='params'>schema:scott</div>
<source lang=sql class='tidy'> DROP TABLE games</source>
<source lang=sql class='setup'> CREATE TABLE emp(
  name VARCHAR(20),
  date date);
INSERT INTO emp VALUES (1,'a','jan,10,2014');
INSERT INTO emp VALUES (2,'b','jan,11,2014');
INSERT INTO emp VALUES (3,'c','jan,10,2014');
INSERT INTO emp VALUES (4,'d','jan,11,2014');
In a GROUP BY statement only <i>distinct</i> values are shown for the column in the GROUP BY.
This example shows the continents hosting the Olympics with the count of the number of games held.
<source lang='sql' class='def'>
SELECT continent, COUNT(yr) FROM games
GROUP BY continent
<p>See also</p>
  <li>[[SUM_and_COUNT |SUM and COUNT]]</li>
  <li>[[SELECT_.._WHERE |SELECT WHERE]]</li>

Revision as of 12:07, 23 April 2014