FIRST AND LASTDAY OF MONTH

SELECT LAST_DAY(:datecol1) FROM  DUAL;


select trunc(trunc(sysdate,'MM')-1,'MM') "First Day of Last Month",trunc(sysdate,'MM')-1 "Last Day of Last Month" from dual


select trunc(trunc(sysdate,'MM')-1,'MM') "First Day of Last Month" FROM DUAL