建表
create table activity ( player_id int, device_id int, event_date date, games_played int ); 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);先找出每个玩家首次登陆的日期，再根据日期找设备名称
select player_id, device_id from activity where (player_id, event_date) in (select player_id, min(event_date) m from activity GROUP BY player_id)