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

The following logic will only count a visit as a 'unique visit' if there wasn't a preceding record from the same ip address within the preceding 10 seconds.

This means that {1,11,21,32,42,52,62,72} will count as 2 visits, with 3 and 5 tracks each, respectively.

It accomplishes this by first identifying the unique visits. Then it counts all visits that happened between that unique visit and the next unique visit.

WITH
    unique_visits
(
  SELECT
    ip_address, time_stamp
  FROM
    visitors
  WHERE
    NOT EXISTS (SELECT * FROM visitors AS [previous]
                WHERE ip_address  = visitors.ip_address
                  AND time_stamp >= visitors.timestamp - 10
                  AND time_stamp <  visitors.timestamp)
)
SELECT
  unique_visitors.ip_address,
  unique_visitors.time_stamp,
  COUNT(*) AS [total_tracks]
FROM
  unique_visitors
INNER JOIN
  visitors
    ON  visitors.ip_address  = unique_visitors.ip_address
    AND visitors.time_stamp >= unique_visitors.time_stamp
    AND visitors.time_stamp <  ISNULL(
                                  (SELECT MIN(time_stamp) FROM unique_visitors [next]
                                   WHERE  ip_address = unique_visitors.ip_address
                                   AND    time_stamp > unique_visitors.ip_address)
                                  , visitors.time_stamp + 1
                               )

You will also want either an index or primary key on (ip_address, time_stamp)