Problems trying to SUM after returning date on first row in all rows

Question

Hi,
I'm having problems with a calculation in a table report.
We've built a Discoverer report that looks at long term absence of an employee. The long-term absence period must be worked out based on a 2-year rolling period from the start date of the employee's most recent sickness. For example, if i'm off sick and have been since 01-Mar-2009 the report will look at all absences i've had since 01-Mar-2007 and sum the days.
I have built a calculation that always returns the latest absence start date for every row of absence a person has had. This has been achieved by using a LEAD Function and ROW_NUMBER, see below:
LEAD(Absence Start Date,ROW_NUMBER() OVER(PARTITION BY Employee Number  ORDER BY  Absence Start Date DESC)-1) OVER(PARTITION BY Employee Number  ORDER BY  Absence Start Date DESC)
The problem I have is that I cannot SUM the Absence Days of the person and bring in one row per person in the report. I think the cause is the use of the ROW_NUMBER. It ends up returning a Row for every absence the person has had.
Is there any way I can achieve returning the latest absence start date of a person against all absence rows (in order to use a condition to restrict the report to all absences that started after 2 years prior to that date) that they've had and sum up the absence days so that only one row per person is returned? I cannot use row generators and cannot register PL/SQL functions. I would need to get IT to help me which is min 3 month turnaround, so I'm trying to resolve this quickly.
Hope you can help.
Many Thanks,
Lloyd

Answer 1

Hi Michael,
Thanks a lot for this. The calculation you provided fixes the issue. However, The partition part of it seems to cause another.
In order to calculate total absence days the following calculation is used:
SUM(CASE WHEN NVL2("Absence (Employee) - Historic"."Date End",( CASE WHEN Absence Finish >= Absence Start THEN "Absence (Employee) - Historic".Absence Days END ),CASE WHEN "Absence (Employee) - Historic".Date Start < Period Start Date THEN WORKING_DAYS_BETWEEN(Period Start Date,Absence Finish) WHEN Absence Finish >= Absence Start THEN WORKING_DAYS_BETWEEN(Absence Start,Absence Finish) END) = 0 THEN DAYS_BETWEEN(Absence Start,Absence Finish) ELSE NVL2("Absence (Employee) - Historic"."Date End",( CASE WHEN Absence Finish >= Absence Start THEN "Absence (Employee) - Historic".Absence Days END ),CASE WHEN Absence Finish >= Absence Start THEN WORKING_DAYS_BETWEEN(Absence Start,Absence Finish) END) END) OVER(PARTITION BY "Person Assignment Information (Person) - Historic".Employee Number ORDER BY "Person Assignment Information (Person) - Historic".Employee Number )
Here is a little Key:
Absence Start
GREATEST("Absence (Employee) - Historic".Date Start,ADD_MONTHS(TRUNC(SYSDATE),-24))
Absence Finish
LEAST(NVL("Absence (Employee) - Historic".Date End,TRUNC(SYSDATE)),TRUNC(SYSDATE))
Period Start Date
ADD_MONTHS(MAX("Absence (Employee) - Historic".Date Start) OVER(PARTITION BY "Absence (Employee) - Historic".Employee Number ORDER BY "Absence (Employee) - Historic".Date Start DESC ),-24)
The item Absence Days is the number of days input against the absence by the user. This is only correct for end-dated absences. For people who have open-ended absence or those whose absence start before the period start date (Michael's date) we must work the days out. A function called WORKING_DAYS_BETWEEN achieves this. There is also another function called DAYS_BETWEEN which is all days between two days (weekends included).
The item Date Start is the absence Start Date, Date End is the Absence End date.
The whole lot is then summed by Employee number partition.
The report has lots of indicators that using mathemical equations based ont Total Absence Days. In order to use Total Absence Days in another mathematical calc I have to create a duplicate calculation except without the partition (Total_Absence_Days in this case). If don't and simply insert the name of the calc into another calculation I get this error when running the report.
Image: !http://www.aerographicsuk.com/Invalid%20Identifier.jpg!
When creating another mathematical calc I then have to do the Sum partition around it. This makes the report run really slow because i'm typing lots of large formulae every time i build a calc that refers to Total Absence Days.
Is there a way I can create the total absence days calculation with out causing this error? I have thought about breaking it up into several calculations but am wondering if i'll get the same error message.
Below is an example of a calculation that tries to use Total Absence Days:
GREATEST("Full Pay Entitlement (Days)"-SUM(Total_Absence_Days) OVER(PARTITION BY "Absence (Employee) - Historic".Employee Number ORDER BY "Absence (Employee) - Historic".Employee Number ),0)
Kranthi, I can only paste in the Oracle SQL, which isn't real SQL. There are lots of other calcs though, so they'll probably be a lot there. Please let me know if you'd like to see it.
Many Thanks for your help with this,
Lloyd