Question

我有一个名为class RegistrationHandler(tornado.web.RequestHandler): def post(self, *args, **kwargs): call_async_register("some params") def call_async_register(parameters): def call(): http_client = AsyncHTTPClient() future = Future() http_request = HTTPRequest(url, request_type.name, headers={'X-Peering': '1'}, body=body) def handle_future(f: Future): future.set_result(f.result()) fetched_future = http_client.fetch(http_request) fetched_future.add_done_callback(handle_future) return future try: instance = io_loop.IOLoop.current() response = instance.run_sync(call) return response.body.decode() except Exception as err: self.logger.exception("Account Request Failed: {}".format(err)) return None的表，该表包含两列：player_ratings和player_id。例如：

rating

我想返回玩家评分最高的玩家列表。

如果表中有重复的行，则返回最上面的行。例如，| player_id | rating | | 1 | 950 | | 1 | 945 | | 2 | 850 | | 2 | 850 | 2具有两行，且同一行player_id，因此返回表中的第3行。

该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，但没有删除重复的行：

rating

实际输出

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 ;

预期输出

 |  player_id     |       ranking       | 
 |     1          |         950         |
 |     2          |         850         |
 |     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中具有唯一的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

如何选择列值最高的行，如果重复则返回最上面的行？

4 个答案: