Generate Days in Month (PIPELINED Functions)

This cool example is not one I can take the credit for but since it is used pretty heavily in our organisation, I thought I would share it as it's not only pretty cool buy also demonstrates how useful Oracle Pipelined functions can be.

In essence a Pipeline table function (introduced in 9i) allow you use a PL/SQL function as the source of a query rather than a physical table. This is really useful in our case to generate all the days in a calendar month via PL/SQL and query them back within our application.

To see this in operation, simply create the following objects:

CREATE OR REPLACE TYPE TABLE_OF_DATES IS TABLE OF DATE;

CREATE OR REPLACE FUNCTION GET_DAYS_IN_MONTH 
(
 pv_start_date_i IN DATE
) 
 RETURN TABLE_OF_DATES PIPELINED 
IS
 lv_working_date DATE;
 lv_days_in_month NUMBER;
 lv_cnt NUMBER;
BEGIN
   
  lv_working_date := TO_DATE(TO_CHAR(pv_start_date_i, 'RRRRMM') || '01', 'RRRRMMDD'); 
  lv_days_in_month := TRUNC(LAST_DAY(lv_working_date)) - TRUNC(lv_working_date);
    
  PIPE ROW(lv_working_date);
  
  FOR lv_cnt IN 1..lv_days_in_month
  LOOP
    lv_working_date := lv_working_date + 1;
    PIPE ROW (lv_working_date);
  END LOOP;
  
  RETURN;

END GET_DAYS_IN_MONTH;
/

Once your objects are successfully complied, you can generate all the days in a month by executing the following query:

SELECT column_value the_date
     , TO_CHAR(column_value, 'DAY') the_day 
  FROM TABLE (get_days_in_month(sysdate));

THE_DATE        THE_DAY
------------------------
01-AUG-09 SATURDAY 
02-AUG-09 SUNDAY   
03-AUG-09 MONDAY   
04-AUG-09 TUESDAY  
05-AUG-09 WEDNESDAY
06-AUG-09 THURSDAY 
07-AUG-09 FRIDAY   
08-AUG-09 SATURDAY 
09-AUG-09 SUNDAY   
10-AUG-09 MONDAY   
11-AUG-09 TUESDAY  
12-AUG-09 WEDNESDAY
13-AUG-09 THURSDAY 
14-AUG-09 FRIDAY   
15-AUG-09 SATURDAY 
16-AUG-09 SUNDAY   
17-AUG-09 MONDAY   
18-AUG-09 TUESDAY  
19-AUG-09 WEDNESDAY
20-AUG-09 THURSDAY 
21-AUG-09 FRIDAY   
22-AUG-09 SATURDAY 
23-AUG-09 SUNDAY   
24-AUG-09 MONDAY   
25-AUG-09 TUESDAY  
26-AUG-09 WEDNESDAY
27-AUG-09 THURSDAY 
28-AUG-09 FRIDAY   
29-AUG-09 SATURDAY 
30-AUG-09 SUNDAY   
31-AUG-09 MONDAY


I hope someone finds this example as useful as we do. The credits go to Simon Hunt on this one as it was "borrowed" from one of his apps. Since I offered to buy him a beer he has promised not to make too big a deal out it :)

As always, you can read up on this topic here

Comments

VinceM said…
Nice use of pipelined functions. You can also do this in pure SQL using something like the following:

with first_day as (
select trunc(sysdate, 'MONTH') the_date from dual
)
select month_dates.the_date, to_char(month_dates.the_date, 'DAY') the_day
from (
select (first_day.the_date + level - 1) the_date
from first_day
connect by rownum <= (last_day(first_day.the_date) - first_day.the_date + 1)
) month_dates
/

Regards...
26 August 2009 at 10:01
Anonymous said…
Does it even need to be that complicated?:

SELECT trunc(sysdate, 'MONTH') + rownum - 1 the_date
FROM all_objects
WHERE rownum <= to_char(last_day(sysdate), 'DD');
17 September 2009 at 16:01
Davide Moraschi said…
I like VinceM solution.
Way faster and cost effective!

nice ONE

BTW, I like the Lake of Como also ;-)
11 November 2009 at 13:06
Neelesh Shah said…
http://www.neelesh.com/2009/12/generate-days-in-month.html
5 December 2009 at 05:34
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