firstdaythismonth, lastdaythismonth, firstdayprevmonth, lastdayprevmonth,days_of_prevmonth

FIRSTDAYTHISMONTH

LASTDAYTHISMONTH

FIRSTDAYPREVMONTH

LASTDAYPREVMONTH

DAYS_OF_PREVMONTH

SELECT Trunc(SYSDATE, 'MM')                            firstdaythismonth,
       Last_day(Trunc(SYSDATE))                        lastdaythismonth,
       Trunc(Trunc(SYSDATE, 'MM') - 1, 'MM')           firstdayprevmonth,
       Last_day(Trunc(Trunc(SYSDATE, 'MM') - 1, 'MM')) lastdayprevmonth,
       Extract(DAY FROM Last_day(Trunc(Trunc(SYSDATE, 'MM') - 1, 'MM')))
                                                       days_of_prevmonth
FROM   dual;