2022-12-13：游戏玩法分析 I。写一条 SQL 查询语句获取每位玩家 第一次登陆平台的日期。 +-----------+-------------+ |

DROP TABLE IF EXISTS `activity`;
CREATE TABLE `activity` (
  `player_id` int(11) NOT NULL,
  `device_id` int(11) NOT NULL,
  `event_date` date NOT NULL,
  `games_played` int(11) NOT NULL,
  UNIQUE KEY `player_id` (`player_id`,`event_date`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

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