Dense_Rank() over order by date fields not working properly

Question

Hi,
i have a pl/sql statement which looks like this:
WITH OrderedByDateTable     AS
     SELECT     gsp.*, DENSE_RANK () OVER (ORDER BY A_varChar_col1,
decode(upper('COMPLIANCETICKSDATE'),'TASKNBR',TASK_NBR,
'DESCRIPTION', DESCRIPTION,
'PARTNBR', PART_NBR,
'PARTSERIALNBR', PART_SERIAL_NBR,
'SORTDATE', TO_DATE(MIN_EST_DUE_DATE),
'COMPLIANCETICKSDATE', COMPLIANCE_DATE,
TASK_NBR
)DESC NULLS LAST,task_nbr,description,enrtask_id)     AS r_num
     FROM     GT_STATUS_PAGING gsp
SELECT     *
FROM     OrderedByDateTable     
The result that i am expecting is that the dense_rank should order the compliance_date column in desc order and finally gives ranks to the rows.
But i am getting the resultset in some order all the time, but it is neither ASC or DESC.
But if for debugging purposes, lets say if i replace the COMPLIANCE_DATE column with DESCRIPTION column again it works perfectly fine giving me the descriptions in DESC order along with the ranks. But for both the date fields above it doesnt work.
Can anyone please help me on how to solve this?

Answer 1

user12270778 wrote:
Hi,
i have a pl/sql statement which looks like this:
The result that i am expecting is that the dense_rank should order the compliance_date column in desc order and finally gives ranks to the rows.
But i am getting the resultset in some order all the time, but it is neither ASC or DESC.
Can anyone please help me on how to solve this?The problem is an implicit date conversion that takes place.
Because the first parameters of your decode are strings, the COMPLIANCE_DATE column is also converted into a string. This string is then sorted alphanumerically. The default format mask is often DD-MON-RR. Therefore your date column would be sorted by day, then by the name of the month and so on.
Fast solution would be to do an explicit conversion from date into strings that match the ordering.
WITH  OrderedByDateTable     AS
        (     SELECT     gsp.*, DENSE_RANK () OVER (ORDER BY  A_varChar_col1,
                     decode(upper('COMPLIANCETICKSDATE'),
                               'TASKNBR',TASK_NBR,
                               'DESCRIPTION', DESCRIPTION,
                               'PARTNBR', PART_NBR,
                               'PARTSERIALNBR', PART_SERIAL_NBR,
                               'SORTDATE', TO_DATE(MIN_EST_DUE_DATE),
                               'COMPLIANCETICKSDATE', to_char(COMPLIANCE_DATE,'YYYYMMDD HH24:MI:SS'), /* this is the important bit */
                               TASK_NBR
                               ) DESC NULLS LAST,task_nbr,description,enrtask_id)     AS r_num
                    FROM     GT_STATUS_PAGING  gsp
SELECT     *
FROM     OrderedByDateTable     You should be careful, because the same problem also happens with your SORTDATE column MIN_EST_DUE_DATE.
Edited by: Sven W. on Oct 25, 2012 6:53 PM