A given date + 1 hour

Question

Hi guys,
I have a quick question for ya that I am hoping is not to hard. I currently have a date time field and basically all I want to do is add 1 hour to this field and was wondering if its as simple as doing + 0.041666.
ie , if i select sysdate + 0.041666 from dual that gives me exactly 1 hour from the current datetime, but I was wondering is there a more accurate way to do this or a different method to do this to ensure it is correct? as 1/24 is actually 0.0416666666666666666667 or whatever I am just curious as to if my method is the correct way to do this.
Thanks.

Answer 1

Hi,
See below query:
select
  i
  ,to_char(d, 'hh:mm:ss') d
  ,to_char(s1, 'hh:mm:ss') s1
  ,to_char(s2, 'hh:mm:ss') s2
from
  dual
model
dimension by (0 x)
measures (0 i, sysdate d, sysdate s1, sysdate s2)
rules
iterate (1e6) until (to_char(d[0], 'ss') != to_char(s2[iteration_number + 1], 'ss') )
s1[iteration_number + 1] = d[0] + (iteration_number + 1) / 24
,s2[iteration_number + 1] = d[0] + (iteration_number + 1) * 0.041666
,i[iteration_number + 1] = iteration_number +1
I D        S1       S2    
0 06:08:58 06:08:58 06:08:58
1          07:08:58 07:08:58
2          08:08:58 08:08:58
3          09:08:58 09:08:58
4          10:08:58 10:08:58
5          11:08:58 11:08:58
6          12:08:58 12:08:58
7          01:08:58 01:08:58
8          02:08:58 02:08:58
9          03:08:58 03:08:57
10 rows selected Explenation:
The above query generates a list of dates (formated in time only). After each iteration of the rules in the model clause we add 1/24 to s1 and 0.041666 to s2.
The iteration is done maximum 1e6 (1 milion) times but when the seconds part of the original date and the date in s2 are not equal we also stop.
You see that after adding only 9 time 0.041666 to a date you have an offset of 1 second already.
I tried with the 1/24 but even after milions of iterations it still has the same number of seconds.
So you see you may not use the 0.041666 if you intend to ad more then 8 hours.
Regards,
Peter