Using with and row_number in a query

Question

I'm trying to do a sub-select on a top N type query, for multiple slices. It works for 1 or 2 slices at a time, but then returns nulls.
with subselect as
select issue, count(*) as cnt, row_number() over (order by count(*) desc) as rn
from TBL
group by issue
select * from
select avg(cnt) as avg1_10 from SUBSELECT
where rn between 1 and 10
select avg(cnt) as avg11_20 from SUBSELECT
where rn between 11 and 20
returns
AVG1_10 AVG11_20
140.5 100
This query works fine, and so does this.
with subselect as
select issue, count(*) as cnt, row_number() over (order by count(*) desc) as rn
from TBL
group by issue
select * from
select avg(cnt) from SUBSELECT
where rn between 21 and 30
select avg(cnt) from SUBSELECT
where rn between 31 and 40
AVG21_30 AVG31_40
70.6 59
but this query:
with subselect as
select issue, count(*) as cnt, row_number() over (order by count(*) desc) as rn
from TBL
group by issue
select * from
select avg(cnt) as avg1_10 from SUBSELECT
where rn between 1 and 10
select avg(cnt) as avg11_20 from SUBSELECT
where rn between 11 and 20
select avg(cnt) from SUBSELECT
where rn between 21 and 30
select avg(cnt) from SUBSELECT
where rn between 31 and 40
returns:
AVG1_10 AVG11_20 AVG21-30 AVG31-40
140.5 100
Does anyone have some insights?
Thank-you, CSW

Answer 1

The initial select returns hundreds of rows.
But I'm even more confused now. The following query
with subselect as
select * from (
select issue, count(*) as cnt, row_number() over (order by count(*) desc) as rn
from TBL
group by issue
)where rownum <= 100)
select * from
select avg(cnt) as avg1_10 from SUBSELECT
where rn between 1 and 10
select avg(cnt) as avg11_20 from SUBSELECT
where rn between 11 and 20
select avg(cnt) from SUBSELECT
where rn between 21 and 30
select avg(cnt) from SUBSELECT
where rn between 31 and 40
select avg(cnt) from SUBSELECT
where rn between 41 and 50
returns:
AVG1_10 AVG11_20 AVG21_30 AVG31_40 AVG41_50
140.5 100 70.6 59 50
Why would limiting the returning rows from the subselect affect the results?
Thanks.