The suggested solution is interesting, but just for those who are interested - another approach with correlated subquery can also be used here:
select Weekend, RevenueInMillions,
(select sum(RevenueInMillions)
from MovieScreening m2
where m2.MovieId = 10 and m2.Weekend <= m1.Weekend) as RunningTotal
from MovieScreening m1
where m1.MovieId = 10;
But window functions are definitely a way to go in such tasks.
Course: https://www.educative.io/collection/5352985413550080/6335716377231360
Lesson: https://www.educative.io/collection/page/5352985413550080/6335716377231360/5327494434521088
Course: https://www.educative.io/collection/5352985413550080/6335716377231360
Lesson: https://www.educative.io/collection/page/5352985413550080/6335716377231360/5327494434521088