单挑力扣（LeetCode）SQL笔试题：511. 游戏玩法分析 I（难度：简单）

活动表Activity：+--------------+---------+| Column Name  | Type    |+--------------+---------+| player_id    | int     || device_id    | int     || event_date   | date    || games_played | int     |+--------------+---------+表的主键是 (player_id, event_date)。这张表展示了一些游戏玩家在游戏平台上的行为活动。每行数据记录了一名玩家在退出平台之前，当天使用同一台设备登录平台后打开的游戏的数目（可能是 0 个）。
写一条 SQL查询语句获取每位玩家 第一次登陆平台的日期。
查询结果的格式如下所示：Activity 表：+-----------+-----------+------------+--------------+| 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 表：+-----------+-------------+| player_id | first_login |+-----------+-------------+| 1         | 2016-03-01  || 2         | 2017-06-25  || 3         | 2016-03-02  |+-----------+-------------+
来源：力扣（LeetCode）链接：https://leetcode.cn/problems/game-play-analysis-i
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#测试数据Create table If Not Exists Activity (player_id int, device_id int, event_date date, games_played int);
insert into Activity (player_id, device_id, event_date, games_played) values ('1', '2', '2016-03-01', '5');insert into Activity (player_id, device_id, event_date, games_played) values ('1', '2', '2016-05-02', '6');insert into Activity (player_id, device_id, event_date, games_played) values ('2', '3', '2017-06-25', '1');insert into Activity (player_id, device_id, event_date, games_played) values ('3', '1', '2016-03-02', '0');insert into Activity (player_id, device_id, event_date, games_played) values ('3', '4', '2018-07-03', '5');
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select    player_id,    min(event_date) first_loginfrom Activitygroup by player_id;
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