Dates that fall on weekday and weekend

Question

Hi everyone, consider the following data i have.
WITH eff_dates AS
SELECT To_Date('1/29/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
SELECT To_Date('2/1/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
SELECT To_Date('2/3/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
SELECT To_Date('2/4/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
SELECT To_Date('2/26/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
SELECT To_Date('3/1/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
SELECT To_Date('3/31/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
SELECT To_Date('4/1/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
SELECT To_Date('4/30/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
SELECT To_Date('5/3/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
SELECT To_Date('5/4/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
SELECT To_Date('5/28/2010','mm/dd/yyyy') c_date FROM dual
output should be
C_DATE
1/29/2010
2/26/2010
3/31/2010
4/30/2010
5/28/2010this is how to get to this output.
i want to display all month end dates. you might already notice that 1/29 and 2/26 and 5/28 are not month end date. however, they fall on the last friday of the
month. so basically i want to display all month end dates that fall on a weekday and if they fall on a weekend, then display the date of the last friday for that
month
can somebody help write a query that produce the output above for the data given?

Answer 1

Try this:
SQL> WITH eff_dates AS
  2  (
  3  SELECT To_Date('1/29/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
  4  SELECT To_Date('2/1/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
  5  SELECT To_Date('2/3/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
  6  SELECT To_Date('2/4/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
  7  SELECT To_Date('2/26/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
  8  SELECT To_Date('3/1/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
  9  SELECT To_Date('3/29/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
10  SELECT To_Date('3/30/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
11  SELECT To_Date('3/31/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
12  SELECT To_Date('4/1/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
13  SELECT To_Date('4/30/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
14  SELECT To_Date('5/3/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
15  SELECT To_Date('5/4/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
16  SELECT To_Date('7/30/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
17  SELECT To_Date('8/27/2010','mm/dd/yyyy') c_date FROM dual UNION ALL
18  SELECT To_Date('5/28/2010','mm/dd/yyyy') c_date FROM dual
19  )
20  select c_date,
21         to_char(c_date, 'DY', 'NLS_DATE_LANGUAGE=ENGLISH') wd_c_date,
22         ld,
23         to_char(ld, 'DY', 'NLS_DATE_LANGUAGE=ENGLISH') wd_ld
24    from (select c_date, last_day(c_date) ld  from eff_dates)
25   where to_char(c_date, 'DY', 'NLS_DATE_LANGUAGE=ENGLISH') in ('MON', 'TUE', 'WED', 'THU', 'FRI')
26         and (c_date = ld or c_date = trunc(ld, 'iw') + 4);
C_DATE      WD_C_DATE LD          WD_LD
29/1/2010   FRI       31/1/2010   SUN
26/2/2010   FRI       28/2/2010   SUN
31/3/2010   WED       31/3/2010   WED
30/4/2010   FRI       30/4/2010   FRI
30/7/2010   FRI       31/7/2010   SAT
SQL> Except that in your sample output I think may 28 may have been a mistake, since may 31 is not on a weekend.