funnel.sql

select distinct user_id 
from events s3
inner join 
(
  select distinct user_id 
  from events s2
  inner join 
  (
    select distinct user_id
    from events
    where event = 'View Product'
    and timestamp between '2017-09-01'::timestamp and now()
  ) s1
  on s1.user_id = s2.user_id
  and s2.timestamp < (s1.timestamp + '7 days'::interval)
  -- and s2.timestamp > s1.timestamp
  where s2.event = 'Add to Cart'
) s2
on s3.user_id = s2.user_id
and s3.timestamp < (s2.timestamp + '7 days'::interval)
-- and s3.timestamp > s2.timestamp
where s3.event = 'Checkout'