Subtracting values for two date ranges.

If you restrict the date range to October, where do you expect the November data to come from?

Can you post the table description and sample data to go with your expected results.
Oracle version would help as well.

Off the top of my head maybe something like:

select oct_def_p, nov_def_p, nov_def_p-oct_def_p diff
from (
Select
sum(case when to_char(date,'MM') = '10' then  DEF_P end) oct_def_p,
sum(case when to_char(date,'MM') = '11' then  DEF_P end) nov_def_p
from xxx
where date between 10/1/2014 and 11/30/2014
);

will you need to do this over more than one month? that is, look for differences between april and may, may and june, june and july,  etc?

If so, try something like this, extend the date range for as long of a period as you need.  Note the date ranges are >=  on the low end and <  (not equal)  on the high end

SELECT m,
       def_p,
       prev_def_p,
       prev_def_p - def_p diff
  FROM (  SELECT TRUNC(yourdate, 'mm') m,
                 SUM(def_p) def_p,
                 LAG(SUM(def_p)) OVER (ORDER BY TRUNC(yourdate, 'mm')) prev_def_p
            FROM xxx
           WHERE yourdate >= TO_DATE('10/1/2014', 'mm/dd/yyyy')
             AND yourdate < TO_DATE('12/1/2014', 'mm/dd/yyyy')
        GROUP BY TRUNC(yourdate, 'mm'))
 WHERE prev_def_p IS NOT NULL

>>I need to be able to compare values from one month to values of another month and get a difference.<<
The simple answer is select valuesfromonemonth - valuesofanothermonth
If valuesfromonemonth is greater than valuesofanothermonth, the result will be positive and, if not, the result will be negative. How you retrieve values for a given month is another question. Your question is a little vague. Perhaps you can provide some sample data and your expected results.

All are great answers - I will look at today and get back with probably more questions and a less vague response also :)

Ok this is the code I have and it shows the percents under column DEF_PCNT for each EMP_Number.  Using the AsofDate that is defined this sql returns values for October.   I need to compare two months.  If November, I need to compare to October.  If December I need to compare to November.  I am comparing what EMP_Numbers had a change in DEF_PCNT and doing a count of those that changed percentages between the months.

Example (if employee 1 changed percents in November then I would count him, if not I would not count him).

So my question remains is there to do this in sql (values from different months and show a count).  Thanks in advance.

Oct
Emp Number       DEF_PCNT                  
1                                       8


Nov
Emp Number       DEF_PCNT                      
1                                       9

_____________________________________________________________________






DEFINE AsOfDate = TO_DATE('11/01/2014','MM/DD/YYYY')

SELECT
Distinct  EMP_Number, DEF_PCNT
FROM(
 SELECT EMP_Number, NVL(DEF_P,0) as DEF_PCNT
FROM yyyy
  LEFT JOIN(
      SELECT PLAN_ID, ACTY_Date,
      n_CUR_CTCH_UP_P + N_CUR_PRE_TAX_SPL_P As DEF_P
        FROM xxx
         ) DFRL ON PART.EMP_ID=DFRL.EMP_ID AND  PART.PLAN_ID=DFRL.PLAN_ID

   AND ACTY_Date Between add_months(&AsOfDate,-1) and (&AsOfDate - 1)
)

will you need to do this over more than one month? that is, look for differences between april and may, may and june, june and july,  etc?

will do just for two months at a time.

and the date value shows as  dd-mmm-yy (01-SEP-14)

WITH monthlydata
     AS (SELECT DISTINCT TRUNC(acty_date, 'mm') mon, emp_number, def_pcnt
           FROM (SELECT emp_number, NVL(def_p, 0) AS def_pcnt
                   FROM yyyy part
                        LEFT JOIN
                        (SELECT plan_id, acty_date, n_cur_ctch_up_p + n_cur_pre_tax_spl_p AS def_p
                           FROM xxx) dfrl
                            ON part.emp_id = dfrl.emp_id
                           AND part.plan_id = dfrl.plan_id
                           AND acty_date >= ADD_MONTHS(TRUNC(&asofdate, 'mm'), -1)
                           AND acty_date < ADD_MONTHS(TRUNC(&asofdate), 1)))
SELECT TO_CHAR(m, 'yyyy-mon') mon,
       def_pcnt,
       prev_def_pcnt,
       prev_def_pcnt - def_pcnt diff
  FROM (  SELECT mon, def_pcnt, LAG(def_pcnt) OVER (ORDER BY mon) prev_def_pcnt
            FROM monthlydata
        GROUP BY mon)
 WHERE prev_def_pcnt IS NOT NULL;


in this query asofdate is for the 2nd month in your 2month span.

So, enter any date in November and you'll Oct and Nov data compared.

change the mon TO_CHAR to whatever format you want


or using the sum(case) method

WITH monthlydata
     AS (SELECT DISTINCT TRUNC(acty_date, 'mm') mon, emp_number, def_pcnt
           FROM (SELECT emp_number, NVL(def_p, 0) AS def_pcnt
                   FROM yyyy part
                        LEFT JOIN
                        (SELECT plan_id, acty_date, n_cur_ctch_up_p + n_cur_pre_tax_spl_p AS def_p
                           FROM xxx) dfrl
                            ON part.emp_id = dfrl.emp_id
                           AND part.plan_id = dfrl.plan_id
                           AND acty_date >= ADD_MONTHS(TRUNC(&asofdate, 'mm'), -1)
                           AND acty_date < ADD_MONTHS(TRUNC(&asofdate), 1)))
SELECT mon1, mon2, mon2 - mon1 diff
  FROM (SELECT SUM(CASE WHEN mon = ADD_MONTHS(TRUNC(&asofdate, 'mm'), -1) THEN def_pcnt END) mon1,
               SUM(CASE WHEN mon = ADD_MONTHS(TRUNC(&asofdate), 1) THEN def_pcnt END) mon2
          FROM monthlydata);

This is my attempt of adding your code --- need help.
This row is adding the percents (   n_CUR_CTCH_UP_P + n_CUR_PRE_TAX_DFRL_P + N_CUR_PRE_TAX_SPL_P As DEF_P) then is referenced as DEF_PCNT


DEFINE AsOfDate = TO_DATE('11/01/2014','MM/DD/YYYY')

SELECT
Distinct SSN_Number, DEF_PCNT, ACTY_Date,
 TO_CHAR(m, 'yyyy-mon') mon,
       def_pcnt,
       prev_def_pcnt,
       prev_def_pcnt - def_pcnt diff
FROM(
 SELECT mon,
def_pcnt,
LAG(def_pcnt) OVER (ORDER BY mon) prev_def_pcnt,
Emp_Number,
NVL(DEF_P,0) as DEF_PCNT, ACTY_Date
FROM monthlydata

  LEFT JOIN(
      SELECT PLAN_ID, SSN_ID, ACTY_Date,
      n_CUR_CTCH_UP_P + n_CUR_PRE_TAX_DFRL_P + N_CUR_PRE_TAX_SPL_P As DEF_P
     
          FROM YYYY
         ) DFRL ON PART.SSN_ID=DFRL.SSN_ID AND  PART.PLAN_ID=DFRL.PLAN_ID

Where prev_def_pcnt IS NOT NULL
    AND DFRL_ACTY_D Between add_months(&AsOfDate,-1) and (&AsOfDate - 1)

Group by mon
)

the WITH clause was part of the solution.

it incorporated your original query, don't change it

just run it as is, except for changing the xxxx and yyyy to your real tables

Ok - I am getting an error that I am missing right parenthesis on this line  "    ON part.EMP_id = dfrl.EMP_id'

I think I fixed the error.  Still checking.

I am having problems with the "mon"   and I need to add a where statement

Where Emp_ID = 1234 from the Part table or the first table.  I am not use to the With statement.  I got the sql to run but I had to take out everywhere the was a "mon."

Maybe I need to change the format for the month -  Like I said had to take out any reference to "mon' to run and need to add where plan_id =.  

DEFINE AsOfDate = TO_DATE('11/01/2014','MM/DD/YYYY')

WITH monthlydata
     AS (SELECT DISTINCT EMP_N, def_pcnt
           FROM (SELECT EMP_N, NVL(def_p, 0) AS def_pcnt
                   FROM dbo.EMP_PART  Part ( get error on this line "missing righ paren"
                    Where PLAN_ID = 204
                        LEFT JOIN (
                        (SELECT plan_id, EMP_ID, ACTY_Date,
                        n_cur_ctch_up_p + n_cur_pre_tax_spl_p AS def_p
                           FROM dbo.V_ACTY_DLY) DFRL
                              ON part.EMP_id = dfrl.EMP_id
                              AND part.plan_id = dfrl.plan_id
                              and DFRL_ACTY_D >= ADD_MONTHS(TRUNC(&asofdate, 'mm'), -1)
                           AND DFRL_ACTY_D < ADD_MONTHS(TRUNC(&asofdate), 1)))
SELECT
       def_pcnt,
       prev_def_pcnt,
       prev_def_pcnt - def_pcnt diff
  FROM (  SELECT def_pcnt, LAG(def_pcnt) OVER (ORDER BY def_pcnt) prev_def_pcnt
            FROM monthlydata
        GROUP BY DEf_pcnt)
 WHERE prev_def_pcnt IS NOT NULL
 )
;

I will add the mon part back - I just needed to see the sql run.  Not sure why it would not run.

With this sql _ I get an error "missing Select" on this line " AND DFRL_ACTY_D < ADD_MONTHS(TRUNC(&asofdate), 1)))"

DEFINE AsOfDate = TO_DATE('11/01/2014','MM/DD/YYYY')
WITH monthlydata
     AS (SELECT DISTINCT TRUNC(ACTY_Date, 'mm') mon, emp_number, def_pcnt
           FROM (SELECT EMP_N, NVL(def_p, 0) AS def_pcnt
                   FROM dbo.V_FDPAT_PART) PART
                        LEFT JOIN
                        (SELECT plan_id, DFRL_ACTY_D, n_cur_ctch_up_p + n_cur_pre_tax_spl_p AS def_p
                           FROM dbo.V_ACTY_DLY) DFRL
                            ON part.EMP_id = dfrl.EMP_id
                           AND part.plan_id = dfrl.plan_id
                           --and Part.PLAN_ID = '204'
                           AND ACTY_Date >= ADD_MONTHS(TRUNC(&asofdate, 'mm'), -1)
                           AND ACTY_Date < ADD_MONTHS(TRUNC(&asofdate), 1)))
SELECT mon1, mon2, mon2 - mon1 diff
  FROM (SELECT SUM(CASE WHEN mon = ADD_MONTHS(TRUNC(&asofdate, 'mm'), -1) THEN def_pcnt END) mon1,
               SUM(CASE WHEN mon = ADD_MONTHS(TRUNC(&asofdate), 1) THEN def_pcnt END) mon2
          FROM monthlydata);

You have an extra closing paran.

WITH monthlydata
     AS (SELECT DISTINCT TRUNC(acty_date, 'mm') mon, emp_number, def_pcnt
           FROM (SELECT emp_n, NVL(def_p, 0) AS def_pcnt
                   FROM dbo.v_fdpat_part part
                        LEFT JOIN
                        (SELECT plan_id,
                                dfrl_acty_d,
                                n_cur_ctch_up_p + n_cur_pre_tax_spl_p AS def_p
                           FROM dbo.v_acty_dly) dfrl
                            ON part.emp_id = dfrl.emp_id
                           AND part.plan_id = dfrl.plan_id
                           --and Part.PLAN_ID = '204'
                           AND acty_date >= ADD_MONTHS(TRUNC(&asofdate, 'mm'), -1)
                           AND acty_date < ADD_MONTHS(TRUNC(&asofdate), 1)))
SELECT mon1, mon2, mon2 - mon1 diff
  FROM (SELECT SUM(CASE WHEN mon = ADD_MONTHS(TRUNC(&asofdate, 'mm'), -1) THEN def_pcnt END) mon1,
               SUM(CASE WHEN mon = ADD_MONTHS(TRUNC(&asofdate), 1) THEN def_pcnt END) mon2
          FROM monthlydata);

Ok - appreciate the staying with me as I need to get this done.  I am now getting an error using the above code
ORA-00904: "ACTY_Date": invalid identifier
00904. 00000 -  "%s: invalid identifier"


the ACTY-DATE field is in the DFRL table only.  

and I was getting an error on this line  "AND acty_date < ADD_MONTHS(TRUNC(&asofdate), 1)))"

and the date field for ACTY_Date is '02-SEP-14'.

Example for each EMP_ID for OCT was there a change in DEF_P from SEPtember
 EMP_ID      ACT_Date          DEF_P
096      22-Sep-14              15


EMP_ID      ACT_Date          DEF_P
096      22-OCT-14        10

I understand.  I appreciate the help and feedback