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POIn SQL how can I use an index to speed up this database query?
 

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  1. POIn SQL how can I use an index to speed up this database query?
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    <p>I have two tables:</p> <p><img src="https://i.stack.imgur.com/Rtnxx.png" alt="enter image description here"></p> <pre><code>CREATE TABLE `album` ( `album_id` int(10) unsigned NOT NULL, `artist_id` int(10) unsigned NOT NULL, `album_type_id` int(10) unsigned NOT NULL, `name` varchar(255) NOT NULL, `first_released` year(4) NOT NULL, `country_id` smallint(5) unsigned DEFAULT NULL, PRIMARY KEY (`album_id`), KEY `artist_id` (`artist_id`), KEY `name` (`name`) ) ENGINE=InnoDB CREATE TABLE `artist` ( `artist_id` int(10) unsigned NOT NULL, `type` enum('Band','Person','Unknown','Combination') NOT NULL, `name` varchar(255) NOT NULL, `gender` enum('Male','Female') DEFAULT NULL, `founded` year(4) DEFAULT NULL, `country_id` smallint(5) unsigned DEFAULT NULL, PRIMARY KEY (`artist_id`), KEY `name` (`name`) ) ENGINE=InnoDB; </code></pre> <p>My first query:<br></p> <pre><code>select ar.name, count(*) from artist ar join album al on ar.artist_id=al.artist_id group by ar.artist_id limit 10; </code></pre> <p>which produces a result set in 0.00 seconds.</p> <p>I would like to order the results, so I add "order by 2 desc":</p> <pre><code>select ar.name, count(*) from artist ar join album al on ar.artist_id=al.artist_id group by ar.artist_id order by 2 desc limit 10; </code></pre> <p>but now the result set takes over 5 seconds, which is too slow.</p> <p>Execution plan: <img src="https://i.stack.imgur.com/xP6wi.png" alt="enter image description here"></p> <p>How can I add an index to speed up my new query?</p> <p>Sample data: <a href="http://bit.ly/1k5ROrT" rel="nofollow noreferrer">http://bit.ly/1k5ROrT</a></p>
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    1. USdavidjhp
    1. USdavidjhp
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    1. COhi @davidjhp, i'm sorry but what `order by 2 desc` will do ?
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      1. POIn SQL how can I use an index to speed up this database query?
      1. USHardy
    2. COThis sorts the result set, by number of albums, in descending order. It provides a list of artists that have the highest number of albums.
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      1. POIn SQL how can I use an index to speed up this database query?
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    3. COWhat does your execution plan look like?
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      1. USalroc
 

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