MySQL：Select 行，最大列值和相应的日期时间由另一列分组

Question

我的table是

IP  HITS    DATETIME
ip1 90      2016-09-10 01:15:37
ip2 13      2016-09-10 04:16:41
ip3 14      2016-09-10 05:17:41
ip2 12      2016-09-10 07:18:42
ip3 45      2016-09-10 09:19:42
ip1 88      2016-09-10 13:20:43
ip2 15      2016-09-10 15:21:43
ip3 26      2016-09-10 18:22:44

结果是

IP  HITS    DATETIME
ip1 90      2016-09-10 01:15:37
ip2 15      2016-09-10 15:21:43
ip3 45      2016-09-10 09:19:42

如有任何建议，我们将不胜感激。

Answer 1

这是使用 Correlated sub-query

的一种方法

select * from yourtable a
where hits = (select max(hits) from yourtable b where a.IP = b.IP)

另一种使用方式JOIN

SELECT a.IP,a.HITS,a.DATETIME
FROM   yourtable a 
       JOIN (SELECT Max(hits) AS max_hits, 
                    ip 
             FROM   yourtable 
             GROUP  BY ip) b 
         ON a.ip = b.ip 
            AND b.max_hits = a.hits

MySQL：Select 行，最大列值和相应的日期时间由另一列分组

MySQL: Select rows with max column value and corresponded datetime grouped by another column

mysql

sql

database

group-by

greatest-n-per-group