Question

I am trying to count events (which are rows in the event_table) in the year before and the year after a particular target date for each person. For example, say I have a person 100 and target date is 10/01/2012. I would like to count events in 9/30/2011-9/30/2012 and in 10/02/2012-9/30/2013.

My query looks like:

select * 
from (
    select id, target_date
    from subsample_table
    ) as i
left join (
   select id, event_date, count(*) as N
        , case when event_date between target_date-365 and target_date-1 then 0 
               when event_date between target_date+1 and target_date+365 then 1
               else 2 end as after 
   from event_table
   group by id, target_date, period
   ) as h
on   i.id = h.id 
 and i.target_date = h.event_date

The output should look something like:

id  target_date  after  N
100 10/01/2012   0      1000
100 10/01/2012   1      0    

It’s possible that some people do not have any events in the before or after periods (or both), and it would be nice to have zeros in that case. I don’t care about the events outside the 730 days.

Any suggestions would be greatly appreciated.

Answer 1

I think the following may approach what you are trying to accomplish.

   select id
         , target_date
         , event_date
         , count(*) as N
         , SUM(case when event_date between target_date-365 and target_date-1 
                    then 1
                    else 0
                end) AS Prior_ 
         , SUM(case when event_date between target_date+1 and target_date+365 
                    then 1
                    else 0
               end) as After_              
      from subsample_table i
      left join 
           event_table h
        on i.id = h.id 
       and i.target_date = h.event_date
     group by id, target_date, period