How to merge two date ranges

Question

Hi,
I have following table. I want to merge date ranges if the dates are continuous and the value is same.I am using Oracle 10g.Please help.
START_DATE END_DATE VALUE
1/1/2008 12/31/2008 1234
1/1/2009 12/31/2009 1234
Sql statement output should be as follows:
START_DATE END_DATE VALUE
1/1/2008 12/31/2009 1234
Thanks in advance.
Edited by: user3898545 on Jan 27, 2010 7:44 PM

Answer 1

Hi,
user3898545 wrote:
create table test_group(emp_id varchar2(5),
start_date date,
end_date date,
value varchar2(10));
insert into test_group(emp_id,start_date,end_date,VALUE) values ('E1','1-JAN-2008','31-DEC-2008','G1');start_date and end_date are DATEs; don't try to put VARCHAR2 values (such as '1-JAN-2008') into DATE columns. Use TO_DATE or DATE literals instead. The INSERT statements you posted may work on your system, but they won't necessarily work anywhere else. In particular, they don't work on my system. Post some sample data that anyone can use.
... I used following query to get the output 1/1/2009 - 12/31/2009 G2 when I ran for any date in 2010 or greater.There can be break in date ranges. Although query is giving the correct output which I am looking for I am looking for better performence.
SELECT MAX (START_DATE)     AS START_DATE,MAX (END_DATE) AS END_DATE ,
MAX(VALUE) KEEP (DENSE_RANK FIRST ORDER BY START_DATE DESC) GROUP_NUMBER
FROM
(WITH     GOT_GRP     AS
(SELECT     TB_TEST_DATA.*,
     END_DATE - SUM (END_DATE + 1 - START_DATE) OVER ( PARTITION BY VALUE
                                        ORDER BY START_DATE) AS GRP
FROM
(SELECT HD.START_DATE,NVL(HD.END_DATE,'31-DEC-9999') "END_DATE",HD.VALUE
FROM test_group HD
WHERE HD.EMP_ID = 'E1'
AND HD.START_DATE < NVL (HD.END_DATE, '31-DEC-9999')
AND HD.END_DATE < :VDT_AS_OF_DATE
ORDER BY EMP_ID,START_DATE) TB_TEST_DATA
SELECT MIN (START_DATE)     AS START_DATE,MAX (END_DATE) AS END_DATE,VALUE
FROM GOT_GRP
GROUP BY VALUE,GRP
ORDER BY START_DATE) CO_GRP;If you have new requirements, maybe you should start a new thread.
What are your new requirements?
When you say "There can be break in date ranges", do you mean grp plays no role in this new problem? In that case, you can save time and effort by not computing it.
The following should produce the results you want from the sampe data given:
WITH     got_r_num     AS
     SELECT     start_date, end_date, value
     ,     ROW_NUMBER () OVER ( ORDER BY start_date  DESC
                        ,           value       DESC
                       )     AS r_num
     FROM     test_group
     WHERE     end_date < TO_DATE ( :vdt_as_of_date
                       , 'DD-MON-YYYY'
SELECT     start_date, end_date, value
FROM     got_r_num
WHERE     r_num     = 1
;