SQL Supports two date/time functions NEXT_ DAY and LAST_DAY using this functions we can find records between dates.

Syntax: NEXT_DAY (, ) 

LAST_DAY (date) 

Options are SUN, MON, TUE, WED, THU, FRI, and SAT

I give some examples which will explain how to find the THIS WEEK, Next WEEK and THIS MONTH, NEXT MONTH.
Note:- Assuming SUNDAY - SATURDAY as week


1) Finding this week dates


WHERE pending_date between TO_CHAR (NEXT_DAY(sysdate - 7, 'SUN'), 'dd-Mon-yyyy') and TO_CHAR (NEXT_DAY(sysdate - 1, 'SAT'), 'dd-Mon-yyyy')


2) Finding next week dates


WHERE pending_date between TO_CHAR (NEXT_DAY(sysdate, 'SUN'), 'dd-Mon-yyyy') and TO_CHAR (NEXT_DAY(sysdate + 6, 'SAT'), 'dd-Mon-yyyy')


3) Finding this month dates


TO_CHAR (TRUNC(sysdate, 'MM'), 'dd-Mon-yyyy') and TO_CHAR (LAST_DAY(sysdate), 'dd-Mon-yyyy')


4) Finding next month dates


TO_CHAR (LAST_DAY(sysdate) + 1, 'dd-Mon-yyyy') and TO_CHAR (LAST_DAY(ADD_MONTHS(sysdate)), 'dd-Mon-yyyy')


Quick Points :


1) LAST_DAY returns last day of the month.
2) NEXT_day returns next occurance of the given week in it.
3) TRUNC(sysdate, 'MM') always returns starting date of the month.
4) ADD_MONTHS(sysdate, 2) adds 2 months to current date. e.g: present month is oct then it will become    DEC. if you use -2 negative number it will reduce in our case it becomes AUG.