sql-date-ranges-accumulative.sql

with source as
(
  select * from ecds_db.playground.time11M
),
timeline as
(
  select id, start_at as happened_at, 1 as balance
  from source
  union all
  select id, end_at as happened_at, -1 as balance
  from source
),
concurrency as
(
  select id, happened_at, balance, sum(balance) over (partition by 1 order by happened_at, id, balance desc rows between unbounded preceding and current row) as count
  from timeline
)
select max(count)
from concurrency