Data Joins and Pivot Help

Question

Hi, I have one fact table and one huge history table that goes really deep with scores stored with month end dates.
I am looking for a way to manipulate the month and year of DateChanged in table A along with joins on the acct no to retrieve scores from previous months, resulting in a de-normalized data format as in the result table.
Any ideas?? Thanks!
Table A
Acct     DateChanged
123     1/12/2008
456     8/25/2008
Table B:
Acct           DateUpload        Score
123           11/30/2007        620
123           12/31/2007        650
123           01/31/2008        712
123           02/29/2008        800
456           05/31/2008        520 
456           06/30/2008        630
456           07/31/2008        680
456           08/31/2008        710
456           09/30/2008        780
456           10/31/2008        786
456           11/30/2008        823
Result Table:
Acct      Score2MonthPrior     Score1MonthPrior
123            620                     650
456            630                     680

Answer 1

If you understood your reqs correctly, it should be:
with a as (
           select 123 acct,to_date('1/12/2008','mm/dd/yyyy') date_changed from dual union all
           select 456,to_date('8/25/2008','mm/dd/yyyy') from dual
     b as (
           select 123 acct,to_date('11/30/2007','mm/dd/yyyy') date_upload,620 score from dual union all
           select 123,to_date('12/31/2007','mm/dd/yyyy'),650 from dual union all
           select 123,to_date('01/31/2008','mm/dd/yyyy'),712 from dual union all
           select 123,to_date('02/29/2008','mm/dd/yyyy'),800 from dual union all
           select 456,to_date('05/31/2008','mm/dd/yyyy'),520 from dual union all
           select 456,to_date('06/30/2008','mm/dd/yyyy'),630 from dual union all
           select 456,to_date('07/31/2008','mm/dd/yyyy'),680 from dual union all
           select 456,to_date('08/31/2008','mm/dd/yyyy'),710 from dual union all
           select 456,to_date('09/30/2008','mm/dd/yyyy'),780 from dual union all
           select 456,to_date('10/31/2008','mm/dd/yyyy'),786 from dual union all
           select 456,to_date('11/30/2008','mm/dd/yyyy'),823 from dual
      c as (
            select  acct,
                    date_upload,
                    score,
                    lead(date_upload,1,sysdate) over(partition by acct order by date_upload) next_date_upload
              from  b
select  acct,
        (select score from c where a.acct = c.acct and add_months(date_changed,-2) >= date_upload and add_months(date_changed,-2) < next_date_upload) Score2MonthPrior,
        (select score from c where a.acct = c.acct and add_months(date_changed,-1) >= date_upload and add_months(date_changed,-1) < next_date_upload) Score1MonthPrior
  from  a
      ACCT SCORE2MONTHPRIOR SCORE1MONTHPRIOR
       123                               620
       456              520              630
SQL> Two months prior 1/12/2008 is 11/12/2007 which falls before the earliest record for acct 123. One month prior 1/12/2008 is 12/12/2007 which falls between 11/30/2007 and 12/31/2007 and therefore score should be 620, not 650.
SY.