Hi,
If you want to guarantee, that adding or substracting a number of months to
the month's end will also result in a month end and if you are already on
release V5R4, you can use the SQL scalar function Add_Months.
Example:
D MyStartDate S D
D MyEndDate S D
*******************************************************************
/Free
MyStartDate = D'2007-05-31';
Exec SQL Set :MyEndDate = Add_Months(:MyStartDate, -3);
Dsply MyEndDate; //--> '2007-02-28'
Exec SQL Set :MyEndDate = Add_Months(:MyEndDate, 3);
Dsply MyEndDate; //--> '2007-05-31'
MyStartDate = D'2007-04-30';
Exec SQL Set :MyEndDate = Add_Months(:MyStartDate, -3);
Dsply MyEndDate; //--> '2007-01-31'
Exec SQL Set :MyEndDate = Add_Months(:MyEndDate, 3);
Dsply MyEndDate; //--> '2007-04-30'
*InLR = *On;
/End-Free
Mit freundlichen Grüßen / Best regards
Birgitta Hauser
"Shoot for the moon, even if you miss, you'll land among the stars." (Les
Brown)
"If you think education is expensive, try ignorance." (Derek Bok)
"What is worse than training your staff and losing them? Not training them
and keeping them!"
-----Ursprüngliche Nachricht-----
Von: rpg400-l-bounces@xxxxxxxxxxxx [
mailto:rpg400-l-bounces@xxxxxxxxxxxx] Im
Auftrag von AGlauser@xxxxxxxxxxxx
Gesendet: Thursday, May 17, 2007 15:59
An: RPG programming on the AS400 / iSeries
Betreff: Re: Months are weird, was '3 Months Ago?'
Booth Martin wrote on 17/05/2007 09:39:50:
What bothers me is that dates don't round trip well. Does March 31st
less one month, plus one month, equal March 31st?
It bothers me too, but I'm not sure there would be a sensible way to
implement month arithmetic so that March 31 could round trip. Suppose
that
a = 2007-03-31
b = a - 1 month + 1 month
If b = a, then you would just have another inconsistency.
c = a - 1 month
d = 2007-02-28
I think that we can agree that c = d. But then you have
c + 1 month = d + 1 month
(a - 1 month) + 1 month = (2007-02-28) + 1 month
2007-03-31 = 2007-02-28 .........................
uh-oh!
Dates arithmetic will never behave like integer arithmetic, because
'months' and 'years' are not really consistently defined.
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