如何从 3 个不同类别中检索 3 个最新记录? [英] How to retrieve 3 latest records from 3 different category?

问题描述

就像我有如下表格:

是否可以从三个类别中获得三个帖子?请帮帮我.

Is it possible to get three posts from three category? Please help me.

推荐答案

You can take the last time stamp of per category -- using max and group by -- order他们按那个时间戳降序排列，并用 limit 取前三名.最后，使用 id 上的连接条件将此结果与原始记录连接起来，这样即使时间戳有关系，您也不会得到三个以上的结果，并输出这些结果.

You could take the last time stamp per category -- using max and group by -- order them by that time stamp in descending order and take the top three with limit. Finally join this result with the original records using a join condition on id so you will not get more than three results, even when there are ties on the time stamp, and output those.

tst 是这里的表名:

select     tst.*
from       tst
inner join (
            select   category, 
                     max(time_stamp) time_stamp,
                     max(id) id
            from     tst
            group by category
            order by 2 desc
            limit    3
           ) as topthree
        on topthree.id = tst.id;

查看它在 rextester

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