Grouping based on ROW_Number of each group

Question

I had a requirement that grouping based on row_number of each group. Please view Image

Answer 1

SQL queries represent unordered sets. So, the distinction between the two groups for 47641 is undefined.

You can define a query that will assign a group that has exactly one fiberid for each scname . When there are multiples, the assignment is arbitrary.

To do so, you can use dense_rank() :

select t.*,
       (dense_rank() over (order by scname) - 1 + 
        row_number() over (partition by scname, fiberid order by fiberid)
       ) as grp
from t;

If you do have an ordering for the rows then a more stable assignment can be calculated.