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POmysql keep last 5 row and remove older records
 

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  1. POmysql keep last 5 row and remove older records
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    <p>I have mysql table with name, and time as filed, I want to select last 5 records for each name. I am not able do this join. any help?</p> <p>sample data</p> <pre><code>CREATE TABLE `ntest` ( `id` int(11) NOT NULL AUTO_INCREMENT, `name` varchar(100) DEFAULT NULL, `updated_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP, PRIMARY KEY (`id`) ) INSERT INTO `ntest` VALUES (1,'java','2012-01-28 21:14:01'), (2,'java','2012-01-28 21:14:03'), (3,'java','2012-01-28 21:14:04'), (4,'perl','2012-01-28 21:14:08'), (5,'perl','2012-01-28 21:14:09'), (6,'perl','2012-01-28 21:14:09'), (7,'perl','2012-01-28 21:14:10'), (8,'perl','2012-01-28 21:14:11'), (9,'perl','2012-01-28 21:14:11'), (10,'perl','2012-01-28 21:14:12'), (11,'perl','2012-01-28 21:14:13'), (12,'perl','2012-01-28 21:14:14'), (13,'mysql','2012-01-28 21:14:21'), (14,'mysql','2012-01-28 21:14:22'), (15,'mysql','2012-01-28 21:14:22'), (16,'mysql','2012-01-28 21:14:23'), (17,'mysql','2012-01-28 21:14:23'), (18,'mysql','2012-01-28 21:14:24'), (19,'mysql','2012-01-28 21:14:25'), (20,'mysql','2012-01-28 21:14:25'), (21,'mysql','2012-01-28 21:14:26'), (22,'mysql','2012-01-28 21:14:26'), (23,'mysql','2012-01-28 21:14:27'), (24,'mysql','2012-01-28 21:14:27'), (25,'php','2012-01-28 21:21:27') </code></pre> <p>from this data I want to displaly. last five java,mysql, perl and php records</p> <p>Edit: based on your answer I came up with sql, but its not working the way I want.</p> <pre><code> select NameCounts.name, NameCounts.updated_at, NameCounts.numnames, @RankSeq := if( @LastDistrict = NameCounts.name, @RankSeq +1, 1 ) DistRankSeq, @LastDistrict := NameCounts.name as ignoreIt from ( select a.name, a.updated_at, count(*) as numnames from ntest a group by a.name, a.updated_at order by a.name, a.updated_at desc ) NameCounts JOIN (select @RankSeq := 0, @LastDistrict = 0 ) SQLVars HAVING DistRankSeq &lt;= 5 </code></pre> <p>Result:</p> <pre><code>+-------+---------------------+----------+-------------+----------+ | name | updated_at | numnames | DistRankSeq | ignoreIt | +-------+---------------------+----------+-------------+----------+ | java | 2012-01-28 19:21:47 | 1 | 1 | java | | java | 2012-01-28 16:14:04 | 1 | 3 | java | | java | 2012-01-28 16:14:03 | 1 | 5 | java | | mysql | 2012-01-28 16:14:27 | 2 | 1 | mysql | | mysql | 2012-01-28 16:14:26 | 2 | 3 | mysql | | mysql | 2012-01-28 16:14:25 | 2 | 5 | mysql | | perl | 2012-01-28 19:22:18 | 1 | 1 | perl | | perl | 2012-01-28 16:14:14 | 1 | 3 | perl | | perl | 2012-01-28 16:14:13 | 1 | 5 | perl | | php | 2012-01-28 19:21:40 | 1 | 1 | php | | php | 2012-01-28 16:21:27 | 1 | 3 | php | +-------+---------------------+----------+-------------+----------+ </code></pre> <p>I expect 5 rows of perl </p> <pre><code>mysql&gt; select * from ntest where name='perl'; +----+------+---------------------+ | id | name | updated_at | +----+------+---------------------+ | 4 | perl | 2012-01-28 16:14:08 | | 6 | perl | 2012-01-28 16:14:09 | | 7 | perl | 2012-01-28 16:14:10 | | 9 | perl | 2012-01-28 16:14:11 | | 10 | perl | 2012-01-28 16:14:12 | | 11 | perl | 2012-01-28 16:14:13 | | 12 | perl | 2012-01-28 16:14:14 | | 28 | perl | 2012-01-28 19:22:18 | +----+------+---------------------+ 8 rows in set (0.00 sec) </code></pre>
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