534. Game Play Analysis III.sql

SELECTa.player_id,a.event_date,SUM(b.games_played)
FROM activity_534 a
JOIN activity_534 b ONa.player_id=b.player_idANDa.event_date>=b.event_date
GROUP BYa.player_id,a.event_date
ORDER BY1,2;

(OR)

SELECT player_id,event_date,
SUM(games_played) OVER w AS games_played
FROM activity_534
WINDOW w AS (PARTITION BY player_id ORDER BY event_date);