如何选择列值最高的行，如果重复则返回最上面的行？

Question

我有一个名为player_ratings的表，该表包含两列： player_id和rating 。 例如：

 |  player_id     |       rating       | 
 |     1          |        950         |
 |     1          |        945         |
 |     2          |        850         |
 |     2          |        850         |

我想返回玩家等级最高的玩家列表。

如果表中有重复的行，则返回最上面的行。 例如， player_id 2有两行具有相同的rating因此请返回表中的第3行。

列表中不应包含任何重复的玩家。 （请参阅预期的输出）

我尝试了以下查询，但它不会删除重复的行：

SELECT * 
FROM player_ratings 
INNER JOIN ( SELECT player_id, MAX(rating) as max_rating FROM player_ratings GROUP BY player_id) topratings 
 ON player_ratings.player_id = topratings.player_id
 AND player_ratings.rating = topratings.max_rating 
ORDER BY player_ratings.rating DESC ;

实际输出

 |  player_id     |       ranking       | 
 |     1          |         950         |
 |     2          |         850         |
 |     2          |         850         |

预期的输出

 |  player_id     |       ranking       | 
 |     1          |         950         |
 |     2          |         850         |

Answer 1

您可以在下面尝试-

   SELECT player_id, MAX(rating) as max_rating FROM player_ratings 
   GROUP BY player_id
   order by max_rating desc

Answer 2

由于只有两列，即玩家ID和排名，您可以简单地进行汇总：

select player_id, max(rating)
from player_ratings
group by player_id
order by max(rating) desc;

Answer 3

假设您在player_ratings具有唯一的ID，则可以执行以下操作：

select pr.*
from player_ratings pr
where pr.player_ratings_id in (select pr2.player_ratings_id
                               from player_ratings pr2
                               where pr2.player_id = pr.player_id
                               order by pr2.max_rating desc, 
                                        pr2.player_ratings_id asc
                              );

Answer 4

使用GROUP BY和MAX()

SELECT player_id, MAX(rating) as Rating
FROM player_ratings GROUP BY player_id
ORDER BY 2 DESC