mysql - 從每個類別中選擇第二個博客

Question

如何從php mysql中的每個類別獲取第二篇文章？

如果我有一個表如下：

post_id | cate_id 
-------------------- 

    1  |  2 
    2  |  4 
    3  |  2 
    4  |  1 
    5  |  1 
    6  |  3 
    7  |  4 
    8  |  3 
    9  |  5 
    10 |  5 

期待的結果如下：

post_id | cate_id 
-------------------- 

    5 |  1 
    3 |  2 
    8 |  3 
    7 |  4 
    10 |  5 

感謝。

Answer 1

SELECT MAX(post_id) post_ID, cate_id 
FROM table1 
GROUP BY cate_id 

Answer 2

select t.cate_id,min(t.post_id) 
from (select cate_id, min(post_id) post_id from foo group by 1) firsts 
inner join foo t on t.cate_id=firsts.cate_id and t.post_id > firsts.post_id 
group by 1; 

考慮：

mysql> select cate_id, group_concat(post_id order by post_id) from foo group by 1; 
+---------+----------------------------------------+ 
| cate_id | group_concat(post_id order by post_id) | 
+---------+----------------------------------------+ 
|  0 | 0,1,3,4,7        | 
|  1 | 0,1,2,4,6,8,9       | 
|  3 | 7,11         | 
|  4 | 2,3         | 
|  5 | 1,3,9         | 
|  6 | 0,2,5,6,7,8,9       | 
|  7 | 0,2         | 
|  8 | 0,1,4,6,7,8,9       | 
|  9 | 1,2         | 
+---------+----------------------------------------+ 

生產：

mysql> select t.cate_id,min(t.post_id) from (select cate_id, min(post_id) post_id from foo group by 1) firsts inner join foo t on t.cate_id=firsts.cate_id and t.post_id > firsts.post_id group by 1; 
+---------+----------------+ 
| cate_id | min(t.post_id) | 
+---------+----------------+ 
|  0 |    1 | 
|  1 |    1 | 
|  3 |    11 | 
|  4 |    3 | 
|  5 |    3 | 
|  6 |    2 | 
|  7 |    2 | 
|  8 |    1 | 
|  9 |    2 | 
+---------+----------------+