Comparing a table itself to find the grade change duration

Question

hi Frnds
I have one table with Grades and jobs and i need to find the duration of staff for a particular grade.If a person have multiple grades in his EmpGrade History how long he was on that grade.I want to find the grade differe not job Difference.How long one person stayed in a certian grade as of 31-DEC- 2007,31-DEC-2008
EmpGradeHist
empno---------grade----------job-------Datestart---------Dateend
110-------------4---------------Clerk------- 01-JAN-2006------01-DEC-2007
110--------------4--------------SnrClerk----02-DEC-2006------01--JAN-2008
110--------------5---------------Officer------02-JAN-2008------31-APR-2009
110-------------6----------------SnrOfficer--- 01-MAy-2009---
111-------------5---------------officer-------01-JAN-2005------01-DEC-2005
110--------------5--------------Snrofficer--02-DEC-2005------31--MAR-2007
110--------------8---------------SnrEXe----01-APR-2007------31-APR-2008
110-------------9----------------SnrExe--------01-MAy-2008--- -
the Desired result should be
as of 31-DEC-2008
empno------ Grade------Dur
110-----------4----------2yrs
110---------- 5----------.9yr
111---------5----------2.3yr
I tried following query but its not working
SELECT empno,grade,MIN(datestart),MAX(dateend),MAX(dateend)-MIN(datestart) Duration FROM
SELECT emp,grade,datestart,(CASE WHEN NVL(dateend,:dt)>=:dt
THEN :dt
                         ELSE dateend END) dateend
FROM EmpGradeHist
WHERE datestart <= :dt)
GROUP BY empno,grade
rgds
radhika

Answer 1

Starting a duplicate thread is not the answer to avoid a question: Comparing a table itself to find the change duration