php - 选择最高的最后一行

Question

我想选择每个成员最高的最后一行。

ID     UID      POINT        DATE           TIME

1       1         5       2012-11-29      11:29:03    
2       2        10       2012-11-29      11:38:12    
3       1        10       2012-12-02      05:15:01    
4       3         5       2012-12-02      09:51:34    
5       2         5       2012-12-02      12:14:14    
6       3         5       2012-12-04      12:18:30
7       1         5       2012-12-05      06:00:51

所以我想选择每个用户最高点的ID，UID和POINT。 结果应该是:

ID     UID      POINT        DATE           TIME

2       2        10       2012-11-29      11:38:12    
3       1        10       2012-12-02      05:15:01      
6       3         5       2012-12-04      12:18:30

我试过这个:

SELECT distinct uid, point, id FROM `test` 
GROUP By uid ORDER BY date DESC, time DESC

和

SELECT id, uid, point FROM `test` 
GROUP BY uid ORDER BY date DESC, time DESC

但是我得到了一些错误的结果:

4(3), 2(2), 1(1)

Answer 1

此查询将为每个用户选择最高分:

select uid, max(`points`)
from members
group by uid

这将选择用户拥有最高分的最大 id:

select uid, max(id)
from members
where (uid, `points`) in (select uid, max(`points`)
                          from members
                          group by uid)
group by uid

这是您需要的最终查询:

select members.*
from members
where (uid, id) in (
  select uid, max(id)
  from members
  where (uid, `points`) in (select uid, max(`points`)
                            from members
                            group by uid)
  group by uid)

显示:

ID  UID  POINT  DATE        TIME
2   2    10     2012-11-29  11:38:12    
3   1    10     2012-12-02  05:15:01      
6   3    5      2012-12-04  12:18:30

这也会给出相同的结果，而且看起来更简单:

SELECT s.*
FROM
  (SELECT members.*
   FROM members
   ORDER BY uid, points desc, id desc) s
GROUP BY uid

我认为它会一直有效，但没有记录在案!

对最后一个查询的一点解释:MySql 允许您通过查询选择组中的非聚合字段。这里我们按 uid 分组但选择所有列:文档说非聚合列的值将是不确定的(它可以是组内的任何值)但是在事实上 MySql 只是返回第一个遇到的值。由于我们在有序子查询上应用非聚合列分组依据，因此第一个遇到的值就是您所需要的。