mysql - 从一列获取相对于另一列数据的数据？

Question

https://docs.google.com/spreadsheet/ccc?key=0Agh6MIWO2pTcdE0yanV0ZkQwWlR6WGxPQUc1T1YtQmc&usp=sharing

MASTER_ID                           END_DATETIME    media_file
1390962109139_635_787802027.    1/29/2014 5:21:41   d:\songs_new\target uganda\welcome56060_l.wav
1390962109139_635_787802027.    1/29/2014 5:21:48   d:\songs_new\target uganda\pending_e.wav
1390962124349_637_788260286.    1/29/2014 5:21:23   d:\songs_new\target uganda\welcome56060_l.wav
1390962199363_744_789334537.    1/29/2014 5:23:03   d:\songs_new\target uganda\welcome56060_l.wav
1390962199363_744_789334537.    1/29/2014 5:23:06   d:\songs_new\target uganda\lang56060mix_l.wav
1390962199363_744_789334537.    1/29/2014 5:23:16   d:\songs_new\target uganda\sub2121_l.wav
1390962199363_744_789334537.    1/29/2014 5:23:03   d:\songs_new\target uganda\welcome56060_l.wav
1390962199363_744_789334537.    1/29/2014 5:23:06   d:\songs_new\target uganda\lang56060mix_l.wav
1390962199363_744_789334537.    1/29/2014 5:23:16   d:\songs_new\target uganda\sub2121_l.wav
1390962205310_742_787802027.    1/29/2014 5:23:13   d:\songs_new\target uganda\welcome56060_l.wav

请查看示例表。我需要获取对应Master_ID的最后播放的媒体文件

例如..

主 ID 1390962109139_635_787802027 所需的数据为 d:\songs_new\target uganda\pending_e.wav

等等...

我使用的是 MySQL 服务器 5.5SQL 约格

Answer 1

因为它是 mysql，所以你可以使用它时髦的分组:

select * from (
    select master_id, media_file
    from mytable
    order by end_datetime desc
) x
group by 1

仅按 master_id 分组意味着 mysql 将为每个 master_id 返回第一行。对数据进行排序意味着返回的行将是最新的。