Query to find the first and last day of month

SELECT TRUNC (ADD_MONTHS (SYSDATE, -1), 'MM') "First Day of Previous Month",

       TRUNC (SYSDATE, 'MM') - 1              "Last Day of Previous Month",

       TRUNC (SYSDATE, 'MM')                  "First Day of Current Month",

       TRUNC (LAST_DAY (SYSDATE))             "Last Day of Current Month"

  FROM DUAL;