Question

我需要基于聚合函数的行中的列。

如果我有一个id的活动列表，我可以获得每个id的最后一个活动的列表，列出id，last_date和相应的活动

CREATE TABLE IF NOT EXISTS `activity_log` (
  `activity_id` int(11) NOT NULL AUTO_INCREMENT PRIMARY KEY,
  `id` int(255) NOT NULL,
  `date_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  `user` varchar(35) NOT NULL,
  `activity` varchar(50) NOT NULL)

SELECT id，activity，max（activity_id）as ma FROM activity_log 按ID分组

返回id并正确返回最后一个日期，但活动不是与max（activity_id）对应的活动

data example

    id  activity   date_time
     1  baseball    2011-8-1
     1  football    2011-8-9
     2  tennis      2011-7-3
     2  hockey      2011-8-9

returns 
    1 baseball 2011-8-9 (I'd like to see football)
    2 tennis   2011-8-9 (I'd like to see hockey)

感谢

Answer 1

尝试一下这样的事情：

Select al.id, al.activity, al.activity_id
From activty_log
Join (Select max(aa.activity_id) as ma From activity_log aa group by aa.id) As al2
 On al2.ma = al2.activity_id;

诀窍是从子查询中共享 id 的每组记录的最大值中获取 activity_id ，然后加入这些结果以获取另一个该特定记录的列。

Answer 2

SELECT id, activity, activity_id as ma FROM activity_log s where not exists (select id from activity_log where id = s.id and s.activity_id < activity_id );

MYSQL - 如何根据聚合列从表中获取非聚合列

2 个答案: