Difference between two rows of a table.

Question

Hi All,
I have a requirement where I need to calculate the difference of a column, but the values are in two rows.
Its exactly like this, I am having a table where in I have stored incidents with their status and their modified dates
example:
Incident_Id : Status : Modified_Date(in seconds from a specific date)
1 : 1 : 9080890
1 : 2 : 9080999
1 : 3 : 9081900
2 : 1 : 10000900
2 : 2 : 10001000
2 : 3 : 10002000
Now the requirement is I have to show the time spent by each incident in each status.
ie for status 1 I need the difference between modified date of status 2 and modified date of status 1 likewise
for status 2 need the difference between modified date of status 3 and modified date of status 2 and so on.
the actual result I need is like this
Incident_Id : Status : Timespent
1: 1: (modified_date(status2) - modified_date(status1))
Please help me to write the query for this.
Regards,
Tauceef

Answer 1

if only you have incremental status (example = 1,2,3, ... )
WITH t (Incident_Id ,Status , Modified_Date) AS (
SELECT 1 , 1 , 9080890 FROM dual UNION ALL
SELECT 1 , 2 , 9080999 FROM dual UNION ALL
SELECT 1 , 3 , 9081900 FROM dual UNION ALL
SELECT 2 , 1 , 10000900 FROM dual UNION ALL
SELECT 2 , 2 , 10001000 FROM dual UNION ALL
SELECT 2 , 3 , 10002000 FROM dual )
SELECT t1.Incident_Id, t1.Status, t1.Modified_Date , t2.Modified_Date-t1.Modified_Date
FROM t t1
LEFT JOIN t t2
ON t2.Incident_Id = t1.Incident_Id
AND t2.status = t1.status+1
ORDER BY 1,2or
there is no need to know what is the next status number :
WITH t (Incident_Id ,Status , Modified_Date) AS (
SELECT 1 , 1 , 9080890 FROM dual UNION ALL
SELECT 1 , 2 , 9080999 FROM dual UNION ALL
SELECT 1 , 3 , 9081900 FROM dual UNION ALL
SELECT 2 , 1 , 10000900 FROM dual UNION ALL
SELECT 2 , 2 , 10001000 FROM dual UNION ALL
SELECT 2 , 3 , 10002000 FROM dual )
SELECT t1.Incident_Id,
       t1.Status,
       t1.Modified_Date ,
       (LEAD(t1.Modified_Date) OVER (PARTITION BY t1.Incident_Id ORDER BY t1.status)) - t1.Modified_Date
FROM t t1Edited by: Ramin Hashimzadeh on May 15, 2013 1:32 PM