Oracle-查询两个日期之间的时差

Question

I am trying to come up with a way in Oracle to calculate the difference between dates in days.

In short. I have two data fields "begins_at" and "ends_at" and the DATA_TYPE for those fields is "TIMESTAMP(6)"

For example. I have the following scenario:

"begins_at" value as “26-MAR-13 02.50.00.000000000 PM”

"ends_at" value as “30-MAR-13 09.25.00.000000000 PM”

I am trying to calculate the different between the two timestamps in days. Is it possible in Oracle?

I tried the following statement but threw an error:

Select TO_DATE(begins_at, 'YYYYMMDD HH:MI:SS AM') - TO_DATE(ends_at, 'YYYYMMDD   HH:MI:SS AM') day_diff

From dual

Any tip is much appreciated.

Answer 1

As our anonymous equine friend noted, 'threw an error' is not helpful. However, it's likely you are getting an ORA-01830, 'date format picture ends before converting entire input string', or ORA-1858, 'a non-numeric character was found where a numeric was expected', or something similar.

The to_date function takes a char argument, so when you pass your timestamp field to it there is an implicit conversion happening; you're essentially doing:

to_date(to_char(begins_at, 'DD-MON-RR'), 'YYYYMMDD HH:MI:SS AM')

... only using your default NLS settings; I'm guessing you're NLS_DATE_FORMAT is set to 'DD-MON-RR' for this example; the exact value will affect the error you get. The format that your timestamp is being given as a string does not match the format you specified for to_date .

You should never rely on implicit conversions, but you don't need to do a conversion here at all. timestamp values can be compared directly, and the results are explained in the documentation . Just subtracting one value form the other will give you the answer as an interval data type:

select ends_at - begins_at from t42;

ENDS_AT-BEGINS_AT
---------------------------------------------------------------------------
+000000004 06:35:00.000000

If you just want the whole day portion you can use extract :

select extract (day from ends_at - begins_at) from t42;

EXTRACT(DAYFROMENDS_AT-BEGINS_AT)
---------------------------------
                                4

You can also treat the timestamp as date using cast :

select cast(ends_at as date) - cast(begins_at as date) from t42;

CAST(ENDS_ATASDATE)-CAST(BEGINS_ATASDATE)
-----------------------------------------
                               4.27430556

I'm not sure why you're using timestamp at all though. The Oracle date type includes a time portion , down to a precision of a second. As you don't (currently) seem to be using the fractional part of the timestamp, sticking to date might make your manipulations simpler, but I guess it depends what you intend to do with these fields later.

Answer 2

See http://docs.oracle.com/cd/E17952_01/refman-5.1-en/date-and-time-functions.html#function_datediff . It describes DATEDIFF , which returns the difference in days, treating only the date values.

Answer 3

Try something like this:

SELECT  TO_DATE('20120125 11:00:00 AM', 'YYYYMMDD HH:MI:SS AM')
     - TO_DATE('20120120 10:00:00 AM', 'YYYYMMDD HH:MI:SS AM') day_diff
FROM   dual

You can refer this . It will really help you

Answer 4

Days, hours, minutes, seconds diff. example - copy/paste to see the output. Replace dates with your dates...:

SELECT start_date, end_date, time_diff,
       EXTRACT(DAY FROM time_diff) days,
       EXTRACT(HOUR FROM time_diff) hours,
       EXTRACT(MINUTE FROM time_diff) minutes,
       EXTRACT(SECOND FROM time_diff) seconds
  FROM
  (
   Select start_date, end_date, (end_date - start_date) time_diff
     From
     (
      Select CAST(to_date('01/01/2012 10:00:00 am', 'dd/mm/yyyy  hh:mi:ss am') AS TIMESTAMP) end_date
           , CAST(to_date('01/01/2012 07:00:00 am', 'dd/mm/yyyy  hh:mi:ss am') AS TIMESTAMP) start_date
       From dual
     )
   )
  /

Subtract time only example:

SELECT trunc(mydate / 3600) hr
     , trunc(mod(mydate, 3600) / 60) mnt
     , trunc(mod(mydate, 3600) / 60 /60) sec
  FROM 
  (
   SELECT (to_date('01/03/2012 10:00:00', 'mm/dd/yyyy  hh24:mi:ss') -
           to_date('01/01/2012 07:00:00', 'mm/dd/yyyy  hh24:mi:ss')) * 86400 mydate
     FROM dual
  )
 /

HR  MNT SEC
-------------
51  0   0