SQL & PL/SQL

Hi everyone...newbie here...but frequent reader (particularly of Mr. Kulash)

So this is what I want to do:  I want to take a set of rows and group them by a specific # per group  (group 1, group 2, etc.)

In the example here it is a set of five rows per group.  Now in reality I won't know the # of records

But I will know:

the # per group

the total # of "complete groups" (where they all have the same # of records)

and based on that the # of records that go into the final group

with a as

(

select level id from dual connect by level <=101  --create X # of rows

),

b as

(

select id

,5 as per_grp

,ceil(count(id) over ()/5)  as t_buckets   -- total # of buckets needed

,trunc(count(id) over ()/5) as s_buckets -- starting # of buckets

from a

),

c as

(

select id

,per_grp

,t_buckets

,s_buckets

,case when id <= (per_grp * s_buckets) then s_buckets end as m_buckets    --maximum # of complete buckets

from b

)

select

id

,per_grp

,t_buckets

,s_buckets

,m_buckets

,case when m_buckets is not null then ntile(m_buckets) over (partition by m_buckets order by id)

else t_buckets

end as final_grp

from c

The final output would be something like this (I cut down the row #'s)

This seems to work, even if the # of records is less than the grouping #.  I guess I 'm looking for guidance.   Is using the Ntile function in a case statement with a null condition a big mistake?  Would there be a better way of doing this?

I originally started here: 

I'm using:

Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production

PL/SQL Release 11.2.0.3.0 - Production

CORE 11.2.0.3.0 Production

TNS for IBM/AIX RISC System/6000: Version 11.2.0.3.0 - Production

NLSRTL Version 11.2.0.3.0 - Production

Any help would be appreciated.

Cheers!