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

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