Question

I would like to rank sequential rows with the null value inside a group of the same natural key. The database is oracle.

Here’s the example :

NAT_KEY      ATTRIBUTE_A        ORDERED_FIELD               RANK
     A                A                     1
     A                                      2                  1
     A                A                     4
     A                I                     6
     A                                      8                  1
     A                                      10                 2
     A                                      11                 3
     B                                      2                  1
     B                                      3                  2
     B                A                     5
     B                A                     6
     B                                      9                  1
     C                A                     1
     C                A                     5
     C                I                     6
     C                                      7                  1
     C                                      8                  2

There must be a way with row_number() function, level and connect by or another one.

Answer 1

I finally figured it out with Andriy M’s link.
Here’s the solution :

select grouped_table.nat_key, 
       grouped_table.attr, 
       grouped_table.order_by,  
       case 
         when attr is null 
           then row_number() over (partition by nat_key, attr, grp order by order_by) 
         else null
       end rowrank 
from (
  select the_table.*, 
         row_number() over (partition by nat_key order by order_by) - row_number() over (partition by nat_key, nvl2(attr, 1, 0) order by order_by) grp 
  from (
    select 'A' nat_key, 'A' attr, 1 order_by from dual 
    union all 
    select 'A' nat_key, null attr, 2 order_by from dual 
    union all 
    select 'A' nat_key, 'A' attr, 4 order_by from dual 
    union all 
    select 'A' nat_key, 'I' attr, 6 order_by from dual 
    union all 
    select 'A' nat_key, null attr, 8 order_by from dual 
    union all 
    select 'A' nat_key, null attr, 10 order_by from dual 
    union all 
    select 'A' nat_key, null attr, 11 order_by from dual 
    union all 
    select 'B' nat_key, null attr, 2 order_by from dual 
    union all 
    select 'B' nat_key, null attr, 3 order_by from dual 
    union all 
    select 'B' nat_key, 'A' attr, 5 order_by from dual 
    union all 
    select 'B' nat_key, 'A' attr, 6 order_by from dual 
    union all 
    select 'B' nat_key, null attr, 9 order_by from dual 
    union all 
    select 'C' nat_key, 'A' attr, 1 order_by from dual 
    union all 
    select 'C' nat_key, 'A' attr, 5 order_by from dual 
    union all 
    select 'C' nat_key, 'I' attr, 6 order_by from dual 
    union all 
    select 'C' nat_key, null attr, 7 order_by from dual 
    union all 
    select 'C' nat_key, null attr, 8 order_by from dual 
  ) the_table 
) grouped_table 
order by nat_key, order_by

Thanks!