获得最后三个用户的所有操作每篇文章

Question

在last Question，我问了一下，从存储用户对deferments的帖子做了所有的操作记录表歌厅的最后三个用户的所有操作，现在我要的是得到相同的东西，但为每个职位。

，通过最后三个用户对每个岗位邓恩的所有操作

history table 
    id  | post_id | action | user_id 
    1  | 5  | 1   | 3 
    1  | 23  | 2   | 1 
    2  | 24  | 2   | 6 
    3  | 34  | 1   | 7 
    4  | 35  | 1   | 1 
    5  | 36  | 1   | 1 
    6  | 23  | 2   | 3 
    7  | 24  | 2   | 1 
    8  | 23  | 1   | 4 
    9  | 24  | 1   | 5 
    10  | 24  | 1   | 1 
    11  | 23  | 1   | 2 
    12  | 23  | 4   | 1 

感谢和抱歉，如果这似乎是一个重复的职位

Answer 1

Coudl这是你在找什么对于？

• SQLFiddle

代码：

SELECT a.user_ID, 
group_concat(a.post_id), 
group_concat(a.action) 
FROM tableName a 
     INNER JOIN 
     (
      SELECT DISTINCT user_ID 
      FROM tableName 
      ORDER BY ID DESC 
      LIMIT 3 
     ) b ON a.user_ID = b.user_ID 
group by a.user_id 
ORDER BY a.User_ID; 


| USER_ID | GROUP_CONCAT(A.POST_ID) | GROUP_CONCAT(A.ACTION) | 
-------------------------------------------------------------- 
|  2 |      7 |      3 | 
|  3 |     5,5,4 |     1,2,5 | 
|  6 |      7 |      2 | 

Answer 2

我认为这将工作：

SELECT a.user_ID, a.post_id, a.action 
FROM tableName a 
     INNER JOIN 
     (
      SELECT DISTINCT 
       @curRow:=IF(@prevRow=post_Id,@curRow+1,1) rn, 
       user_ID, 
       Post_Id, 
       @prevRow:=Post_Id 
      FROM (
       SELECT DISTINCT Post_Id, User_Id 
       FROM TableName 
       ORDER BY Post_Id, ID DESC 
      ) t 
       JOIN (SELECT @curRow:= 0) r 

     ) b ON a.post_id = b.post_id AND a.user_id = b.user_id 
WHERE b.rn <= 3 
ORDER BY a.post_id, a.User_ID 

而且Fiddle。