I had to implement a year diff function which works similarly to sybase datediff. In that case the real year difference is counted, not the rounded day difference. So if there are two dates separated by one day, the year difference can be 1 (see select datediff(year, '20141231', '20150101')
).
If the year diff has to be counted this way then use:
EXTRACT(YEAR FROM date_to) - EXTRACT(YEAR FROM date_from)
Just for the log the (almost) complete datediff function:
CREATE OR REPLACE FUNCTION datediff (datepart IN VARCHAR2, date_from IN DATE, date_to IN DATE)
RETURN NUMBER
AS
diff NUMBER;
BEGIN
diff := CASE datepart
WHEN 'day' THEN TRUNC(date_to,'DD') - TRUNC(date_from, 'DD')
WHEN 'week' THEN (TRUNC(date_to,'DAY') - TRUNC(date_from, 'DAY')) / 7
WHEN 'month' THEN MONTHS_BETWEEN(TRUNC(date_to, 'MONTH'), TRUNC(date_from, 'MONTH'))
WHEN 'year' THEN EXTRACT(YEAR FROM date_to) - EXTRACT(YEAR FROM date_from)
END;
RETURN diff;
END;";
If you just want the difference in years, there's:
SELECT EXTRACT(YEAR FROM date1) - EXTRACT(YEAR FROM date2) FROM mytable
Or do you want fractional years as well?
SELECT (date1 - date2) / 365.242199 FROM mytable
365.242199 is 1 year in days, according to Google.
For Oracle SQL Developer I was able to calculate the difference in years using the below line of SQL. This was to get Years that were within 0 to 10 years difference. You can do a case like shown in some of the other responses to handle your ifs as well. Happy Coding!
TRUNC((MONTHS_BETWEEN(<DATE_ONE>, <DATE_TWO>) * 31) / 365) > 0 and TRUNC((MONTHS_BETWEEN(<DATE_ONE>, <DATE_TWO>) * 31) / 365) < 10
Need to find difference in year, if leap year the a year is of 366 days.
I dont work in oracle much, please make this better. Here is how I did:
SELECT CASE
WHEN ( (fromisleapyear = 'Y') AND (frommonth < 3))
OR ( (toisleapyear = 'Y') AND (tomonth > 2)) THEN
datedif / 366
ELSE
datedif / 365
END
yeardifference
FROM (SELECT datedif,
frommonth,
tomonth,
CASE
WHEN ( (MOD (fromyear, 4) = 0)
AND (MOD (fromyear, 100) <> 0)
OR (MOD (fromyear, 400) = 0)) THEN
'Y'
END
fromisleapyear,
CASE
WHEN ( (MOD (toyear, 4) = 0) AND (MOD (toyear, 100) <> 0)
OR (MOD (toyear, 400) = 0)) THEN
'Y'
END
toisleapyear
FROM (SELECT (:todate - :fromdate) AS datedif,
TO_CHAR (:fromdate, 'YYYY') AS fromyear,
TO_CHAR (:fromdate, 'MM') AS frommonth,
TO_CHAR (:todate, 'YYYY') AS toyear,
TO_CHAR (:todate, 'MM') AS tomonth
FROM DUAL))
Source: Stackoverflow.com