mysql - SQL group by 返回错误数据

Question

这让我疯了！Musing MySQL DBMS（抱歉没有指定）......

我有下表：

"id", "pingdate", "players"
"3","2012-05-24 11:45:04","63"
"1","2012-05-24 12:15:03","14"
"2","2012-05-24 12:15:03","38"
"3","2012-05-24 12:15:03","24"
"1","2012-05-24 12:45:04","22"
"2","2012-05-24 12:45:04","40"
"3","2012-05-24 12:45:04","66"
"1","2012-05-24 13:15:03","14"
"5","2012-05-24 13:15:03","99"
"3","2012-05-24 13:15:03","63"
"3","2012-05-24 13:15:03","38"
"4","2012-05-24 13:15:03","63"

我想要以下结果：

"5","2012-05-24 13:15:03","99"
"3","2012-05-24 12:45:04","66"
"4","2012-05-24 13:15:03","63"

在文本中，我想要 3 个不同的 ID，具有最高玩家和正确的 pingdate。

我已经尝试过了，但它返回了错误的 pingdate：

SELECT id, 
       pingdate, 
       max(players) AS players 
FROM pings 
GROUP BY id  
ORDER BY players DESC 
LIMIT 3

Answer 1

您没有指定 DBMS，所以这是一个 ANSI SQL 解决方案：

select *
from (
    select id, 
           pingdate,
           rank() over (partition by id order by players desc) as rnk
    from pings
) t
where rnk <= 3
order by players desc

Answer 2

您必须使用连接或子查询来完成，请参阅sql - 从基于组的行中获取 id

Select  a.id, a.pingdate, a.players from pings a, (
  SELECT id, max(players) AS players 
  FROM pings 
  GROUP BY id ) b 
where a.id=b.id and a.players=b.players 
ORDER BY players DESC 
LIMIT 3

Answer 3

首先你需要返回所有结果......然后只返回 3

SELECT *
FROM (
SELECT id,pingdate, max(players) AS players 
FROM pings 
GROUP BY id, pingdate  )
WHERE rownum = 3
ORDER BY players DESC 

我希望这能帮到您

Answer 4

最大值 := 的定义没有更高的值：

SELECT id, pingdate, players 
FROM pings pi
    WHERE NOT EXISTS (
         SELECT *
         FROM pings nx
         WHERE nx.id = pi.id
         AND nx.players > pi.players
         )
ORDER BY players
LIMIT 3
    ;