Question

我需要的是为每个unique player_id获取最新的（按日期时间）table_id

表：

buyin_id   player_id   table_id       date_time
---------|-----------|----------|--------------------|
    1    |    10     |    21    | 2015-01-26 00:00:01
    2    |    11     |    21    | 2015-01-26 00:00:02
    3    |    12     |    21    | 2015-01-26 00:00:03
    4    |    10     |    21    | 2015-01-26 00:00:04
    5    |    11     |    21    | 2015-01-26 00:00:05
    6    |    12     |    22    | 2015-01-26 00:00:06
    7    |    13     |    22    | 2015-01-26 00:00:07
    8    |    13     |    22    | 2015-01-26 00:00:08

期望的结果：

buyin_id   player_id   table_id       date_time
---------|-----------|----------|--------------------|
    3    |    12     |    21    | 2015-01-26 00:00:03
    4    |    10     |    21    | 2015-01-26 00:00:04
    5    |    11     |    21    | 2015-01-26 00:00:05
    6    |    12     |    22    | 2015-01-26 00:00:06
    8    |    13     |    22    | 2015-01-26 00:00:08

我尝试了类似这样的东西，每个table_id只返回1行而不是1行

SELECT pb.buyin_id, pb.player_id, pb.buyin, pb.cashout, pb.cashout_error, pb.date_time
FROM poker_buyin AS pb
INNER JOIN (SELECT player_id, MAX(date_time) AS MaxDateTime
FROM poker_buyin GROUP BY player_id) groupedpb 
ON pb.player_id = groupedpb.player_id 
AND pb.date_time = groupedpb.MaxDateTime
WHERE pb.player_id = '$player_id'";

Answer 1

您提到的查询会查找每个玩家ID的最新记录。然后你过滤它只找到一个玩家，所以你得到一行。

如果你想找到每个玩家和桌子的最新记录，你的内部查询需要是：

            SELECT  MAX(buyin_id) buyin_id
              FROM  poker_buyin
             GROUP  BY player_id, table_id

这将从表中获取代表最新播放器/表组合的行ID。

然后你用它来从你的表中提取记录，如（http://sqlfiddle.com/#!2/be68b7/2/0）

SELECT whatever_columns
  FROM poker_buyin
 WHERE buyin_id IN
       (
            SELECT  MAX(buyin_id) buyin_id
              FROM  poker_buyin
             GROUP  BY player_id, table_id
       )
 WHERE player_id = '$player_id'
 ORDER BY player_id, table_id

此查询中有一个小技巧：buyin_id值不断上升，因此这是为每种组合选择最新时间记录的好方法。

Answer 2

如果您在简单的结果列中不需要buyin_id：

SELECT DISTINCT player_id, table_id, max(date_time) as dt 
FROM `poker_buyin ` 
GROUP BY player_id, table_id

mysql按日期时间选择一列中的所有唯一行和另一列中的所有最大行

2 个答案: