Count number of rows that are not within 10 seconds of each other

Question

I track web visitors. I store the IP address as well as the timestamp of the visit.

ip_address    time_stamp
180.2.79.3  1301654105
180.2.79.3  1301654106
180.2.         


        

Answer 1

Make a left join against the records with the same ip and a close time, and filter out the records where there is a match:

select count(*) as visits
from (
  select t.ip_address
  from tracking t
  left join tracking t2
    on t2.ip_address = t.ip_address
    and t2.timestamp > t.timestamp and t2.timestamp <= t.timestamp + 10
  where t2.ip_address is null
) x