Difference between revisions of "Aggregates with DISTINCT"
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(Created page with " <h3>Nobel database</h3> <h2>COUNT DISTINCT</h2> <p>You can find the number of <i>different</i> values using COUNT with DISTINCT</p> <p>In 1915 four prizes were award...") |
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<p>You can find the number of <i>different</i> values using COUNT with DISTINCT</p> | <p>You can find the number of <i>different</i> values using COUNT with DISTINCT</p> | ||
<p>In 1915 four prizes were awarded in three different subjects:</p> | <p>In 1915 four prizes were awarded in three different subjects:</p> | ||
| − | <table | + | <table><td><pre>SELECT yr, subject, winner |
FROM nobel | FROM nobel | ||
WHERE yr=1915</pre> | WHERE yr=1915</pre> | ||
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<td>William Bragg</td> | <td>William Bragg</td> | ||
</tr> | </tr> | ||
| − | </table></td | + | </table></td> |
</table> | </table> | ||
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SELECT COUNT(subject), COUNT(DISTINCT subject) | SELECT COUNT(subject), COUNT(DISTINCT subject) | ||
FROM nobel | FROM nobel | ||
| − | WHERE yr = 1915 | + | WHERE yr = 1915 |
</source> | </source> | ||
</div> | </div> | ||
Revision as of 09:59, 11 July 2012
Nobel database
COUNT DISTINCT
You can find the number of different values using COUNT with DISTINCT
In 1915 four prizes were awarded in three different subjects:
SELECT yr, subject, winner FROM nobel WHERE yr=1915 |
|
COUNT(subject) gives 4; COUNT(DISTINCT subject) gives 3.
SELECT COUNT(subject), COUNT(DISTINCT subject) FROM nobel WHERE yr = 1915
SELECT COUNT(subject), COUNT(DISTINCT subject) FROM nobel WHERE yr = 1915
