Group Record Number for consecutive Rows with same value.

Question

I have following Data in TEST table
END_DATE      HOURS
====================
8/30/2012     20
7/30/2012     30
7/1/2012 30     
6/30/2012     20
5/30/2012     20
5/1/2012     20
I would like to get the following result (GRP_REC_NUM column)
END_DATE      HOURS GRP_REC_NUM
============================
8/30/2012     20 1
7/30/2012     30 1
7/1/2012 30     2
6/30/2012     20 1 *<<----- This should reset back to 1*
5/30/2012     20 2
5/1/2012     20 3
Thanks
slokam

Answer 1

slokam wrote:
I would like to get the following result (GRP_REC_NUM column)
END_DATE      HOURS GRP_REC_NUM
============================
8/30/2012     20 1
7/30/2012     30 1
7/1/2012 30     2
6/30/2012     20 1 *<<----- This should reset back to 1*
5/30/2012     20 2
5/1/2012     20 3
I could not understand why 5/30/2012 has the Rec_num column as 2. According to my understanding, you are trying to assign Ranks to each of the Dates. And if it is so, then 7/1/2012 should have GROUP_REC_NUM as 1 and 7/30/2012 as 2.
Since, it is not clear about the logic to assign ranks, it will be helpful (for you as well as us) if you can elaborate the logic.
Below is probably what you need.
with data as
select to_date('08/30/2012', 'MM/DD/YYYY') dt, 20 hrs from dual union all
select to_date('07/30/2012', 'MM/DD/YYYY') dt, 30 hrs from dual union all
select to_date('07/1/2012', 'MM/DD/YYYY') dt, 30 hrs from dual union all
select to_date('06/30/2012', 'MM/DD/YYYY') dt, 20 hrs from dual union all
select to_date('05/30/2012', 'MM/DD/YYYY') dt, 20 hrs from dual union all
select to_date('05/1/2012', 'MM/DD/YYYY') dt, 20 hrs from dual
select dt, hrs,
       dense_rank() over (partition by to_char(dt, 'MM') order by dt) rn
  from data
order by dt;
DT                        HRS                    RN                    
01-MAY-12                 20                     1                     
30-MAY-12                 20                     2                     
30-JUN-12                 20                     1                     
01-JUL-12                 30                     1                     
30-JUL-12                 30                     2                     
30-AUG-12                 20                     1