mysql - 如何从 user 和 usermeta 表中选择最后一个用户信息？

Question

我使用的是 mysql，我有两个表格如下:

User:
user_id - user_name - phone

UserMeta:
user_meta_id - user_id - meta_key - meta_value - meta_date

我有如下一些记录:

user_id: 23  
meta_key: gender  
meta_value: male  
meta_date: 1534533650



user_id: 23  
meta_key: city  
meta_value: london  
meta_date: 1534533650



user_id: 23  
meta_key: name  
meta_value: jack  
meta_date: 1534533650  



user_id: 25  
meta_key: name  
meta_value: Jamie 
meta_date: 1534593881  

user_id: 25  
meta_key: gender  
meta_value: male 
meta_date: 1534593881  

user_id: 23  
meta_key: gender  
meta_value: female  
meta_date: 1534595971

user_id: 23  
meta_key: city  
meta_value: liverpool  
meta_date: 1534595971 

And ...

我需要获取所有用户信息 (user_id = 23) 并注册了最新更改，例如:

user_id: 23  
meta_key: name  
meta_value: Jamie  
meta_date: 1534533650 

user_id: 23  
meta_key: city  
meta_value: liverpool  
meta_date: 1534595971  

user_id: 23  
meta_key: gender  
meta_value: female  
meta_date: 1534595971  

这个操作的查询很复杂，我很困惑，请帮助我，
我用了这个但没有得到正确的结果:

    "SELECT kmu.*
            FROM user_meta kmu
            INNER JOIN
            (SELECT `meta_key`, `meta_value`, MAX(`meta_date`) AS MaxDateTime
            FROM user_meta
            GROUP BY meta_key) groupedtt
            ON user_id=:id
            AND kmu.meta_key = groupedtt.meta_key
            AND kmu.meta_date = groupedtt.MaxDateTime";

Answer 1

您可以使用以下内容:

SELECT `user`.*, user_meta.meta_key, user_meta.meta_value, user_meta.meta_date 
FROM `user` INNER JOIN (
    SELECT user_id, meta_key, MAX(meta_date) AS meta_date 
    FROM user_meta 
    GROUP BY user_id, meta_key
) meta_select ON `user`.user_id = meta_select.user_id 
INNER JOIN user_meta ON meta_select.meta_key = user_meta.meta_key 
    AND meta_select.user_id = user_meta.user_id 
    AND meta_select.meta_date = user_meta.meta_date
WHERE `user`.user_id = 23

demo: https://www.db-fiddle.com/f/euqvGNW6PguCG495Yi9dTa/1