Date functions in sql

Date functions are used to process data present in the date format. 

Function Description
ADD_MONTHS(d,n)

Adds n months to date.

example: add_months('17-may-99',22)= 17-jul-99

LAST_DAY(d)

Specifies the date of the last day of  month.

example: last_day('17-may-99') = 31-mqy-99

MONTHS_BETWEEN(d1,d2) Specifies the number of months between two dates, d1 and d2. If d2 is more than d1, it returns negative value.
NEXT_DAY(d,char)

Returns the date of the first day of week named by char thaat is equal to or later than the date. suppose you want to find wednesday after date 20-DEC--99,then you can call this function as shown in the following example.

next_day('20-DEC-99', 'wed') = 22-dec-99

TRUNC(value,timeunit) Truncate date according to unit of time.
EXTRACT(FMT FROM DATE) Extracts time component from a date expression