512. 游戏玩法分析 II-优快云博客

本文链接：https://blog.youkuaiyun.com/komonder/article/details/126093749

这是一个关于SQL查询的问题，目标是从Activity表格中找出每个玩家第一次登录时所使用的设备ID。查询利用了窗口函数rank() over (partition by player_id order by event_date)，通过排名找出每个玩家最早的登录日期对应的设备。查询结果展示在Resulttable中，列出了player_id和对应的device_id。

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Table: Activity

+--------------+---------+
| Column Name  | Type    |
+--------------+---------+
| player_id    | int     |
| device_id    | int     |
| event_date   | date    |
| games_played | int     |
+--------------+---------+
(player_id, event_date) 是这个表的两个主键
这个表显示的是某些游戏玩家的游戏活动情况
每一行是在某天使用某个设备登出之前登录并玩多个游戏（可能为0）的玩家的记录

请编写一个 SQL 查询，描述每一个玩家首次登陆的设备名称

查询结果格式在以下示例中：

Activity table:
+-----------+-----------+------------+--------------+
| player_id | device_id | event_date | games_played |
+-----------+-----------+------------+--------------+
| 1         | 2         | 2016-03-01 | 5            |
| 1         | 2         | 2016-05-02 | 6            |
| 2         | 3         | 2017-06-25 | 1            |
| 3         | 1         | 2016-03-02 | 0            |
| 3         | 4         | 2018-07-03 | 5            |
+-----------+-----------+------------+--------------+

Result table:
+-----------+-----------+
| player_id | device_id |
+-----------+-----------+
| 1         | 2         |
| 2         | 3         |
| 3         | 1         |
+-----------+-----------+

drop table if EXISTS activity;
CREATE TABLE If Not Exists activity (player_id INT, device_id INT, event_date DATE, games_played INT, PRIMARY KEY (player_id, event_date));
Truncate table  activity;
INSERT INTO Activity VALUES(1,2,'2016-03-01',5);
INSERT INTO Activity VALUES(1,2,'2016-05-02',6);
INSERT INTO Activity VALUES(2,3,'2017-06-25',1);
INSERT INTO Activity VALUES(3,1,'2016-03-02',0);
INSERT INTO Activity VALUES(3,4,'2018-07-03',5);

select player_id ,device_id
from (
select player_id ,event_date,device_id,
rank() over(partition by player_id order by event_date) rk
from Activity
) tmp
where rk = 1

//这个就不能用分组最值法了