Using pl/sql function for each day between two dates.

Question

Hi,
create TABLE EMP(
ID_EMP NUMBER,
DT_FROM DATE,
DT_TO DATE,
CREATE_DATE DATE);
into EMP(ID_EMP, DT_FROM, DT_TO, CREATE_DATE)
Values(100, TO_DATE('07/01/2008 00:00:00', 'MM/DD/YYYY HH24:MI:SS'), TO_DATE('04/30/2010 00:00:00', 'MM/DD/YYYY HH24:MI:SS'),TO_DATE('05/08/2009 14:11:21', 'MM/DD/YYYY HH24:MI:SS'));
I have a function called  elig_pay_dates(date p_date), which returns the code for  person payment eligibility for a particular date. For paid dates it's 'P' and for unpaid dates it's 'N'.
How can I check this function between two dates for each day. Example : 07/01/2008 to 04/30/2010.
By using this function with select I needs to display the dates when there is a change in status.
I am expecting data in following manner from above logic(this is example):
07/01/2008 --- 07/01/2009 ---'P'
07/02/2009 -- 07/25/2009 ----'N'
07/26/2009 -- 01/01/2010 ---'P'
01/02/2010 -- 01/13/2010 --'N'
01/14/2010 -- 01/18/2010 --'P'
01/19/2010 -- 04/30/2010 -- 'N'
I thought of looping for each day date but that seems to be expensive for online application. Is there any way that I can achieve this requirement with sql query ?
Thanks for your help,

Answer 1

Certainly not the best way to code the requirement, but it does achieve the result you are looking for in a fairly quick time
create or replace
function test_ret_paid_unpaid (p_date in date)
return varchar2
is
  v_ret     varchar2(1);
begin
  if ( (p_date between to_date('07/02/2009', 'MM/DD/YYYY') and to_date('07/25/2009', 'MM/DD/YYYY') ) or
       (p_date between to_date('01/02/2010', 'MM/DD/YYYY') and to_date('01/13/2010', 'MM/DD/YYYY') ) or
       (p_date between to_date('01/19/2010', 'MM/DD/YYYY') and to_date('04/30/2010', 'MM/DD/YYYY') )
    then v_ret := 'N';
  else
    v_ret := 'Y';
  end if;
  return v_ret;
end;
Wrote file afiedt.buf
  1  with get_paid_unpaid as
  2  (
  3    select dt_from start_date, dt_to end_date, dt_from + level - 1 curr_date, test_ret_paid_unpaid(dt_from + level - 1) paid_unpaid,
  4           row_number() over (order by dt_from + level - 1) rn_start,
  5           row_number() over (order by dt_from + level - 1 desc) rn_end
  6      from test_emp
  7    connect by level <= dt_to - dt_from + 1
  8  ),
  9  get_stop_date as
10  (
11  select start_date init_date, end_date, curr_date, paid_unpaid,
12         case when paid_unpaid != lag(paid_unpaid) over (order by curr_date) or rn_start = 1 or rn_end = 1
13          then curr_date
14          else null
15         end start_date,
16         case when paid_unpaid != lead(paid_unpaid) over (order by curr_date) or rn_start = 1 or rn_end = 1
17          then curr_date
18          else null
19         end stop_date
20    from get_paid_unpaid
21  )
22  select period, paid_unpaid
23    from (
24  select init_date, curr_date, start_date, end_date, stop_date,
25         case when paid_unpaid = lead(paid_unpaid) over (order by curr_date)
26                then nvl(start_date, init_date) || ' - ' || lead(stop_date, 1, end_date) over (order by curr_date)
27              else null
28         end period,
29         paid_unpaid
30    from get_stop_date
31   where stop_date is not null or start_date is not null
32         )
33*  where period is not null
12:06:10 SQL> /
PERIOD                                             PAID_UNPAID
01-JUL-08 - 01-JUL-09                              Y
02-JUL-09 - 25-JUL-09                              N
26-JUL-09 - 01-JAN-10                              Y
02-JAN-10 - 13-JAN-10                              N
14-JAN-10 - 18-JAN-10                              Y
19-JAN-10 - 30-APR-10                              N
6 rows selected.
Elapsed: 00:00:00.35