How to calculate difference between two dates in oracle 11g SQL

When I am trying to calculate the date difference by using datediff function it showing that invalid identifier.

SELECT DATEDIFF(day,'2008-08-05','2008-06-05') AS DiffDate from da_static_trade.

Error : invalid identifier.

Can you please tell me what is the function to calculate date difference.

There is no DATEDIFF() function in Oracle. On Oracle, it is an arithmetic issue

select DATE1-DATE2 from table

Oracle support Mathematical Subtract - operator on Data datatype. You may directly put in select clause following statement:

to_char (s.last_upd – s.created, ‘999999D99′)

Check the EXAMPLE for more visibility.

In case you need the output in termes of hours, then the below might help;

Select to_number(substr(numtodsinterval([END_TIME]-[START_TIME]),’day’,2,9))*24 +
to_number(substr(numtodsinterval([END_TIME]-[START_TIME],’day’),12,2))
||':’||to_number(substr(numtodsinterval([END_TIME]-[START_TIME],’day’),15,2)) 
from [TABLE_NAME];

You can not use DATEDIFF but you can use this (if columns are not date type):

SELECT 
to_date('2008-08-05','YYYY-MM-DD')-to_date('2008-06-05','YYYY-MM-DD') 
AS DiffDate from dual

you can see the sample

http://sqlfiddle.com/#!4/d41d8/34609

You can use this:

SET FEEDBACK OFF;
SET SERVEROUTPUT ON;

DECLARE
  V_START_DATE  CHAR(17) := '28/03/16 17:20:00';
  V_END_DATE    CHAR(17) := '30/03/16 17:50:10';
  V_DATE_DIFF   VARCHAR2(17);

BEGIN

SELECT
  (TO_NUMBER( SUBSTR(NUMTODSINTERVAL(TO_DATE(V_END_DATE , 'DD/MM/YY HH24:MI:SS') - TO_DATE(V_START_DATE, 'DD/MM/YY HH24:MI:SS'), 'DAY'), 02, 9)) * 24) +
  (TO_NUMBER( SUBSTR(NUMTODSINTERVAL(TO_DATE(V_END_DATE , 'DD/MM/YY HH24:MI:SS') - TO_DATE(V_START_DATE, 'DD/MM/YY HH24:MI:SS'), 'DAY'), 12, 2)))  || 
              SUBSTR(NUMTODSINTERVAL(TO_DATE(V_END_DATE , 'DD/MM/YY HH24:MI:SS') - TO_DATE(V_START_DATE, 'DD/MM/YY HH24:MI:SS'), 'DAY'), 14, 6) AS "HH24:MI:SS"
  INTO V_DATE_DIFF
FROM 
  DUAL;

DBMS_OUTPUT.PUT_LINE(V_DATE_DIFF);
END;

basically the to_char(sysdate,'DDD') returns no of days from 1-jan-yyyy to sysdate so that if subtract two dates it will return that,you will get difference between two dates

select to_char(sysdate,'DDD') -to_char(to_date('19-08-1995','dd-mm-yyyy'),'DDD') from dual;

Oracle DateDiff is from a different product, probably mysql (which is now owned by Oracle).

The difference between two dates (in oracle's usual database product) is in days (which can have fractional parts). Factor by 24 to get hours, 24*60 to get minutes, 24*60*60 to get seconds (that's as small as dates go). The math is 100% accurate for dates within a couple of hundred years or so. E.g. to get the date one second before midnight of today, you could say

select trunc(sysdate) - 1/24/60/60 from dual;

That means "the time right now", truncated to be just the date (i.e. the midnight that occurred this morning). Then it subtracts a number which is the fraction of 1 day that measures one second. That gives you the date from the previous day with the time component of 23:59:59.

来源：https://stackoverflow.com/questions/25620592/how-to-calculate-difference-between-two-dates-in-oracle-11g-sql

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