1. 累加
力扣534：
关键点：
sum(games_played) over(partition by player_id order by event_date)
--滑动累加求和，指向性明显，用sum()...over()...窗口函数。
注：order by 后省略 rows between，默认rows between unbounded preceding and current row；
order by, rows between 均省略，默认 rows between unbounded preceding and unbounded following。
题解：
select player_id,event_date,
sum(games_played) over(partition by player_id order by event_date)
as games_played_so_far
from Activity
order by player_id,event_date desc
-END
标签：rows,窗口,函数,order,player,between,id,综训,event From： https://www.cnblogs.com/peitongshi/p/16942592.html