Oracle Date Substraction

Question

Hi all,
I have a question regarding Date substraction. I've read somewhere that the standard unit of Date Substraction of Oracle is days. However my requirements is to have result format in hours. Example:
Date1: 1/21/2010 08:00:00 AM
Date2: 1/22/2010 10:00:00 AM
Date2 - Date1 = 1 (day). If I need to convert to hours, I can achieve by multiply it by 24. But in fact the result for this should be 26 hours.
1 more example for this:
Date1: 1/21/2010 08:00:00 AM
Date2: 1/21/2010 10:00:00 AM
Date2 - Date1 - 0 (day). While in fact it should be 2 hours.
In short, I want Date substraction to give me result in hours rather than days. Is there anyway to achieve this objective using pure SQL in Oracle? or do I have to manipulate using some kind of programming language?
I've received a reply from the other thread saying that I could get the number of hours by mulitply the number of days by 24. This is true only if Oracle stores data in format like: 1.2 days after substraction. Is this the case with Oracle?
Thank you very much.
Thanh.

Answer 1

babaravi wrote:
use extract function. you can achieve it.
1  SELECT EXTRACT(HOUR FROM
2  (SYSTIMESTAMP - TO_TIMESTAMP('30.07.2009 10:00:00', 'DD.MM.YYYY HH24:MI:SS'))) AS hour
3* FROM   dual
SQL> /
HOUR
23
SQL>
?:|
The OP asked for Date substraction, not timestamps. Also, your solution doesn't give the total number of hours between the date/times...
SQL> ed
Wrote file afiedt.buf
  1  SELECT EXTRACT(HOUR FROM
  2  (SYSTIMESTAMP - TO_TIMESTAMP('30.07.2009 10:00:00', 'DD.MM.YYYY HH24:MI:SS'))) AS hour
  3* FROM   dual
SQL> /
      HOUR
        22
SQL> ed
Wrote file afiedt.buf
  1  SELECT (SYSDATE - TO_DATE('30.07.2009 10:00:00', 'DD.MM.YYYY HH24:MI:SS'))*24 AS hour
  2* FROM   dual
SQL> /
      HOUR
6982.25944
SQL>Just a slight difference. ;)