oracle本月的最后一天 和第一天

SELECT LAST_DAY(TO_DATE(TO_CHAR(LAST_DAY(SYSDATE), 'YYYY-MM-DD'))) + 1 - 1 / (24 * 60 * 60) AS "本月最后一天"
FROM DUAL;


SELECT TO_DATE(TO_CHAR(TRUNC(SYSDATE, 'MM'), 'yyyy-mm-dd')) AS "本月第一天" FROM dual;