Setting a sequential number to records placed into groups?

Question

Hello I have one table with records which can be grouped and I want to know if I can set an ordinal number to each record and when the group breaks set 1 again to the first record of the group and then 2 to next...3 to next....until group breaks again.....
the first thing I need is order the records according the group then number each record inside the group sequentially from 1 to ..n (numbers or records of the group).
Can I do this???
Thanks in advance

Answer 1

Hello
you can use the row_number analytic function
WITH gp AS
(   SELECT 1 id, 1 family_id,to_date('29/06/1966','dd/mm/yyyy') dob from dual union all
    SELECT 2 id, 1 family_id,to_date('22/06/1986','dd/mm/yyyy') dob from dual union all
    SELECT 3 id, 2 family_id,to_date('04/03/1975','dd/mm/yyyy') dob from dual union all
    SELECT 4 id, 3 family_id,to_date('01/04/1990','dd/mm/yyyy') dob from dual union all
    SELECT 5 id, 3 family_id,to_date('10/01/1996','dd/mm/yyyy') dob from dual union all
    SELECT 6 id, 3 family_id,to_date('21/09/2000','dd/mm/yyyy') dob from dual
SELECT
    id,
    family_id,
    dob,
    ROW_NUMBER() OVER(PARTITION BY family_id ORDER BY DOB) rn,
    ROW_NUMBER() OVER(PARTITION BY family_id ORDER BY DOB DESC) rn_desc
FROM
    gp
        ID  FAMILY_ID DOB                          RN    RN_DESC
         1          1 29-JUN-1966 00:00:00          1          2
         2          1 22-JUN-1986 00:00:00          2          1
         3          2 04-MAR-1975 00:00:00          1          1
         4          3 01-APR-1990 00:00:00          1          3
         5          3 10-JAN-1996 00:00:00          2          2
         6          3 21-SEP-2000 00:00:00          3          1
6 rows selected.which gives you the ability to generate the numbers as you have requested. The important parts are the PARTITION which is the group of rows over which the function will be applied, and the ORDER BY which will determine the order in which the function is applied to those rows. You can see that I called the function twice, once with ORDER BY DOB and the other with ORDER BY DOB DESC and the difference in the output.
HTH
David