从MySQL表中获取最新的更新值

Question

我有一个具有以下结构和数据的mysql表。我想在任何ID上显示最后插入的记录。

id lc_counter  lc_timestamp 
1  15    2013-03-01 11:54:43 
1  13    2013-03-01 11:48:56 
10 7    2013-03-01 11:54:43 
10 5    2013-03-01 11:48:56 
100 5    2013-03-01 11:54:43 
100 3    2013-03-01 11:54:43 


SELECT inv_id, lc_counter, lc_timestamp 
FROM link_counter 
group by inv_id 
order by inv_id asc, lc_timestamp desc 

我想要得到这样的结果：

id lc_counter  lc_timestamp 
1  15    2013-03-01 11:54:43 
10 7    2013-03-01 11:54:43 
100 5    2013-03-01 11:54:43 

Answer 1

Select link_counter.lc_counter, MAX(link_counter.lc_timestamp) 
from link_counter group by link_counter.id 

Answer 2

SELECT 
    inv_id, lc_counter, lc_timestamp 
FROM 
    link_counter A 
WHERE 
    lc_counter >= ALL(
    SELECT 
     lc_counter 
    FROM 
     link_counter B 
    WHERE 
     B.inv_id = A.inv_id 
) 
ORDER BY 
    1 

有一段时间没有这样做，而是应该工作。

Answer 3

如果您没有2个相同的lc_timestamp记录为特定的id下面将给你你想要的确切结果。

select lc.id, lc.lc_counter, lc.lc_timestamp from link_counter lc inner join 
(select id, max(lc_timestamp) as lc_timestamp from link_counter group by id) as lc2 
on lc.id = lc2.id and lc.lc_timestamp = lc2.lc_timestamp order by lc.id asc, lc.lc_timestamp desc;; 

group by本身不会匹配lc_counter。所以，它需要手动匹配。请参阅此fiddle。