Question

我从表player_info中选择，并且使用表player_map_info的列time_played的max（sum（））行。 player_map_info的主键是（player_id，color，map），我希望在所有地图上获得播放时间最多的颜色。

我使用以下查询：

SELECT A.*, 
       B.color AS main_color, 
       B.maxtp 
FROM   player_info A 
       LEFT OUTER JOIN (SELECT E.player_id, 
                               E.color, 
                               Max(sumtp) AS maxtp 
                        FROM   player_map_info C 
                               LEFT OUTER JOIN (SELECT player_id, 
                                                       color, 
                                                       Sum(time_played) AS sumtp 
                                                FROM   player_map_info 
                                                GROUP  BY player_id, 
                                                          color) E 
                                            ON C.player_id = E.player_id 
                                               AND C.color = E.color 
                        GROUP  BY E.player_id) B 
                    ON A.player_id = B.player_id 
WHERE  A.user_id = :user_id

我正在使用SQLite。在我的数据库上执行此操作只需不到0.1秒。

问题：有没有办法让这个查询执行得更快？（我对加入等所有细微差别都很陌生。）

Answer 1

只需取出与用户相关的内容：

SELECT C.color, maxtp 
FROM   player_map_info C 
inner join (SELECT max(time_played) AS maxtp 
                FROM   player_map_info 
                ) mx
) B ON c.time_played = mx.maxtp

内部查询mx获取最大time_played，外部查询连接回它以获取颜色。获得最多的颜色。

让它更快。好吧，在0.1秒时你不太可能做出任何大的增加。

干杯 -

SQL - 选择具有最大总和，效率的行

1 个答案: