LeetCode刷题-数据库（MySQL）- 511.Game Play Analysis I

511.Game Play Analysis I

一、题目描述

Table: Activity

Column Name	Type
player_id	int
device_id	int
event_date	date
games_played	int

(player_id, event_date) is the primary key of this table.
This table shows the activity of players of some game.
Each row is a record of a player who logged in and played a number of games (possibly 0) before logging out on some day using some device.

Write an SQL query that reports the first login date for each player.

The query result format is in the following example:

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	first_login
1	2016-03-01
2	2017-06-25
3	2016-03-02

二、思路分析

对player_id进行GROUP BY，然后使用min()函数找出最早的日期即为首次登录日期。

三、代码实现

SELECT
	player_id,
	min(event_date) AS first_login
FROM
	Activity
GROUP BY player_id;