Oracle: how to add minutes to a timestamp?

I need to add 30 minutes to values in a Oracle date column. I do this in my SELECT statement by specifying "to_char(date_and_time + (.000694 * 31)", which works fine most of the time. But not when the time is on the AM/PM border. For example, adding 30 minutes to "12:30" [which is PM] returns "1:00" which is AM. The answer I expect is "13:00". What's the correct way to do this?

From stackoverflow

• Be sure that Oracle understands that the starting time is PM, and to specify the HH24 format mask for the final output.

  SELECT to_char((to_date('12:40 PM', 'HH:MI AM') + (1/24/60) * 30), 'HH24:MI') as time
    FROM dual
  
  TIME
  ---------
  13:10
  

  Note: the 'AM' in the HH:MI is just the placeholder for the AM/PM meridian indicator. Could be also 'PM'

• If the data type of the field is date or timestamp, Oracle should always give the correct result if you add the correct number given in number of days (or a the correct fraction of a day in your case). So if you are trying to bump the value in 30 minutes, you should use :

  select field + 0.5/24 from table;
  

  Based on the information you provided, I believe this is what you tried to do and I am quite sure it works.

  Sajee : The above answer w/o using to_char on it provides just the default format, eg: 04-NOV-08. Which is not what I'm looking for.

• In addition to being able to add a number of days to a date, you can use interval data types assuming you are on 9i or later, which can be somewhat easier to read,

  SQL> ed
  Wrote file afiedt.buf
  
    1  SELECT sysdate, sysdate + interval '30' minute
    2*   FROM dual
  SQL> /
  
  SYSDATE              SYSDATE+INTERVAL'30'
  -------------------- --------------------
  02-NOV-2008 16:21:40 02-NOV-2008 16:51:40
  

  David Oneill : +1 This was what I was looking for!

  wheelibin : +1 Wow, I never knew this...I can finally drop the ridiculous fractions of a day stuff!

• Based on what you're asking for, you want the HH24:MI format for to_char.

• All of the other answers are basically right but I don't think anyone's directly answered your original question.

  Assuming that "date_and_time" in your example is a column with type DATE or TIMESTAMP, I think you just need to change this:

  to_char(date_and_time + (.000694 * 31))
  

  to this:

  to_char(date_and_time + (.000694 * 31), 'DD-MON-YYYY HH24:MI')
  

  It sounds like your default date format uses the "HH" code for the hour, not "HH24".

  Also, I think your constant term is both confusing and imprecise. I guess what you did is calculate that (.000694) is about the value of a minute, and you are multiplying it by the number of minutes you want to add (31 in the example, although you said 30 in the text).

  I would also start with a day and divide it into the units you want within your code. In this case, (1/48) would be 30 minutes; or if you wanted to break it up for clarity, you could write ( (1/24) * (1/2) ).

  This would avoid rounding errors (except for those inherent in floating point which should be meaningless here) and is clearer, at least to me.

• Thank you to everyone. This is VERY useful!

• from http://www.orafaq.com/faq/how_does_one_add_a_day_hour_minute_second_to_a_date_value

  The SYSDATE pseudo-column shows the current system date and time. Adding 1 to SYSDATE will advance the date by 1 day. Use fractions to add hours, minutes or seconds to the date

  SQL> select sysdate, sysdate+1/24, sysdate +1/1440, sysdate + 1/86400 from dual;
  
  SYSDATE              SYSDATE+1/24         SYSDATE+1/1440       SYSDATE+1/86400
  -------------------- -------------------- -------------------- --------------------
  03-Jul-2002 08:32:12 03-Jul-2002 09:32:12 03-Jul-2002 08:33:12 03-Jul-2002 08:32:13