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

Let me start with this table. I'll use ordinary timestamps so we can easily see what's going on.

180.2.79.3   2011-01-01 08:00:00
180.2.79.3   2011-01-01 08:00:09
180.2.79.3   2011-01-01 08:00:20
180.2.79.3   2011-01-01 08:00:23
180.2.79.3   2011-01-01 08:00:25
180.2.79.3   2011-01-01 08:00:40
180.2.79.4   2011-01-01 08:00:00
180.2.79.4   2011-01-01 08:00:13
180.2.79.4   2011-01-01 08:00:23
180.2.79.4   2011-01-01 08:00:25
180.2.79.4   2011-01-01 08:00:27
180.2.79.4   2011-01-01 08:00:29
180.2.79.4   2011-01-01 08:00:50

If I understand you correctly, you want to count these like this.

180.2.79.3   3
180.2.79.4   3

You can do that for each ip_address by selecting the maximum timestamp that is both

• greater than the current row's timestamp, and
• less than or equal to 10 seconds greater than the current row's timestamp.

Taking these two criteria together will introduce some nulls, which turn out to be really useful.

select ip_address, 
       t_s.time_stamp, 
       (select max(t.time_stamp) 
        from t_s t 
        where t.ip_address = t_s.ip_address 
          and t.time_stamp > t_s.time_stamp
          and t.time_stamp - t_s.time_stamp <= interval '10' second) next_page
from t_s 
group by ip_address, t_s.time_stamp
order by ip_address, t_s.time_stamp;

ip_address   time_stamp            next_page
180.2.79.3   2011-01-01 08:00:00   2011-01-01 08:00:09
180.2.79.3   2011-01-01 08:00:09   <null>
180.2.79.3   2011-01-01 08:00:20   2011-01-01 08:00:25
180.2.79.3   2011-01-01 08:00:23   2011-01-01 08:00:25
180.2.79.3   2011-01-01 08:00:25   <null>
180.2.79.3   2011-01-01 08:00:40   <null>
180.2.79.4   2011-01-01 08:00:00   <null>
180.2.79.4   2011-01-01 08:00:13   2011-01-01 08:00:23
180.2.79.4   2011-01-01 08:00:23   2011-01-01 08:00:29
180.2.79.4   2011-01-01 08:00:25   2011-01-01 08:00:29
180.2.79.4   2011-01-01 08:00:27   2011-01-01 08:00:29
180.2.79.4   2011-01-01 08:00:29   <null>
180.2.79.4   2011-01-01 08:00:50   <null>

The timestamp that marks the end of a visit has a null for its own next_page. That's because no timestamp is less than or equal to time_stamp + 10 seconds for that row.

To get a count, I'd probably create a view and count the nulls.

select ip_address, count(*)
from t_s_visits 
where next_page is null
group by ip_address

180.2.79.3   3
180.2.79.4   3

Answer 2

You could JOIN the tracking table to itself and filter out the records you don't need by adding a WHEREclause.

SELECT  t1.ip_address
        , COUNT(*) AS tracks
FROM    tracking t1
        LEFT OUTER JOIN tracking t2 ON t2.ip_address = t1.ip_address
                                       AND t2.time_stamp < t1.time_stamp + 10
WHERE   t2.ip_adress IS NULL
GROUP BY
        t1.ip_address

Edit

Following script works in SQL Server but I can't express it in a single SQL statement, let alone convert it to MySQL. It might give you some pointers on what is needed though.

Note: I assume for given inputs, number 1 and 11 should get chosen.

;WITH q (number) AS (
  SELECT 1
  UNION ALL SELECT 2
  UNION ALL SELECT 10
  UNION ALL SELECT 11  
  UNION ALL SELECT 12
)
SELECT  q1.Number as n1
        , q2.Number as n2
        , 0 as Done
INTO    #Temp
FROM    q q1
        LEFT OUTER JOIN q q2 ON q2.number < q1.number + 10
                                AND q2.number > q1.number

DECLARE @n1 INTEGER
DECLARE @n2 INTEGER

WHILE EXISTS (SELECT * FROM #Temp WHERE Done = 0)
BEGIN

  SELECT  TOP 1 @n1 = n1
          , @n2= n2
  FROM    #Temp
  WHERE   Done = 0

  DELETE  FROM #Temp
  WHERE   n1 = @n2

  UPDATE  #Temp 
  SET     Done = 1
  WHERE   n1 = @n1 
          AND n2 = @n2         
END        

SELECT  DISTINCT n1 
FROM    #Temp

DROP TABLE #Temp