Connect by Level using count value from record collection

Question

Hello:
PROBLEM:
) y,(select rownum MonthNo from dual connect by level <= Cnt)
Causes ORA-00904 Invalid identifier. Why can’t I use “Cnt” from my main query as using a constant works?
The count value is determined for each date range in How can I return the records I need?
Thanks, Sidney
BACKGROUND:
I need to be able to display a list of tax returns to my users and the status of those returns. Physical returns do not exist so it is necessary to create the data records dynamically using appropriate selects. This is not difficult and I thought I could then just use a connect by level to give me the date information so I could calculate and display the individual returns. However oracle is giving me an ORA-00904 when I try to send the “Cnt” value to connect by level. Everything works fine when I provide a constant instead of “CNT”. The “CNT” value is determined by a complex process that computes the start and stop dates for multiple return types, etc. as well as the number of periods and filing frequency. The data has to be dynamically generated using a master record which then yields the coding history from which my basic record collection is selected. Here is the result of that process:
TaxpayerNo,TaxClass,TaxCode,FilingFequency,StartDate,StopDate,Cnt,Frequency
10 S 1 M 6/1/2007 11/30/2008 18 12
10 S 2 M 11/30/2008 9/30/2009 10 12
10 S 2 Q 11/30/2010 8/18/2011 3 4
10 L 8 A 6/1/2007 9/30/2009 3 1
10 L 8 A 11/30/2010 8/18/2011 1 1
From this data, I need a record for each individual month,quarter,etc. ie:
10 S 1 M 6/1/2007 11/30/2008 18 12 6/1/2007
10 S 1 M 6/1/2007 11/30/2008 18 12 7/1/2007
10 S 1 M 6/1/2007 11/30/2008 18 12 8/1/2007
10 S 1 M 6/1/2007 11/30/2008 18 12 9/1/2007
10 S 2 M 11/30/2008 9/30/2009 10 12 11/30/2008
10 S 2 M 11/30/2008 9/30/2009 10 12 12/30/2008
etc.
DOES NOT WORK
select y.*,MonthNo,Add_Months(StartDate,MonthNo*Frequency) from (
select x.*,
(case when FilingFrequency = 'M' then Ceil(Months_Between(StopDate,StartDate))
when FilingFrequency = 'Q' then Ceil(Months_Between(StopDate,StartDate)/3)
when FilingFrequency = 'A' then Ceil(Months_Between(StopDate,StartDate)/12)
else 0
end) Cnt,
(case when FilingFrequency = 'M' then 1
when FilingFrequency = 'Q' then 3
when FilingFrequency = 'A' then 12
end) Frequency
from (
... complex code to calculate the values of the start and stop dates needed above...
) x
) y,(select rownum MonthNo from dual connect by level <= Cnt)
ERROR MESSAGE
This returns ORA-00904: "CNT": Invalid Identifier. I don't get an error if I use a constant:
WORKS USING A CONSTANT BUT MUST HAVE THE ACTUAL CNT VALUE
... Same code to generate data ...
) y,(select rownum MonthNo from dual connect by level <= 3)
How can I get this to work using the "CNT" value instead of a constant?

Answer 1

A technique like this should fix your problem.
TUBBY_TUBBZ?with data (col1, cnt) as
  2  (
  3    select 1, 3 from dual
  4      union all
  5    select 2, 2 from dual
  6  )
  7  select
  8    d.col1,
  9    t.column_value
10  from
11    data  d,
12    table(cast(multiset(select level from dual connect by level <= d.cnt) as sys.OdciNumberList)) t;
              COL1       COLUMN_VALUE
                 1                  1
                 1                  2
                 1                  3
                 2                  1
                 2                  2
5 rows selected.
Elapsed: 00:00:00.00
TUBBY_TUBBZ?As opposed to what you have now, which is basically this
TUBBY_TUBBZ?with data (col1, cnt) as
  2  (
  3    select 1, 3 from dual
  4      union all
  5    select 2, 2 from dual
  6  )
  7  select
  8    d.col1,
  9    level
10  from
11    data  d
12  connect by level <= d.cnt;
              COL1              LEVEL
                 1                  1
                 1                  2
                 1                  3
                 2                  2
                 1                  3
                 2                  1
                 1                  2
                 1                  3
                 2                  2
                 1                  3
10 rows selected.
Elapsed: 00:00:00.00
TUBBY_TUBBZ?