选择一列中具有非空值的最新记录 [英] SELECT the newest record with a non null value in one column

问题描述

我有看起来像这样的表格数据

I have table data which looks like this

id | keyword | count | date
1 | ipod | 200 | 2009-08-02
2 | ipod | 250 | 2009-09-01
3 | ipod | 150 | 2009-09-04
4 | ipod | NULL | 2009-09-07

现在我所追求的是获取具有最新日期但计数不为空的行的计数.在这种情况下，第 3 行的计数为 150.)

Now what I am after is getting the count of the row which has the newest date but has a not null count. In which case row 3 with count 150.)

例如

SELECT `keyword`, `count` , max( `date` ) 
FROM `keywords` 
WHERE keyword = "ipod"
AND `count` IS NOT NULL 
GROUP BY keyword

这返回了正确的日期，但没有正确的计数(返回 200).我也试过对它自己做一个左连接.

This returned the right date but not the right count (returned 200). I also tried doing a left join on it's self.

SELECT `t1`.`keyword` , `t2`.`count` , max( `t1`.`id` )
FROM `keywords` `t1`
LEFT JOIN `keywords` `t2` ON `t1`.`id` = `t2`.`id`
WHERE `t1`.`keyword` = 'ipod'
AND `t1`.`count` IS NOT NULL
GROUP BY `t1`.`keyword`

这确实获得了最大 id，但它没有像我希望的那样左加入那个，只返回 200.

And this did get the max id but it didn't left-join onto that like I hoped and returned only 200.

帮助?

推荐答案

SELECT `keyword`, `count` , `date`
FROM `keywords` 
WHERE keyword = "ipod"
AND `count` IS NOT NULL 
order by date desc 
limit 1

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