本月第一天
select to_char(trunc(sysdate, 'mm'),'yyyy-mm-dd') from dual;
本月最后一天
select to_char(last_day(trunc(sysdate)),'yyyy-mm-dd') from dual;
下月第一天
SELECT to_char(last_day(SYSDATE) + 1,'yyyy-mm-dd') FROM dual;
下月最后一天
select to_char(last_day(add_months(trunc(sysdate),1)),'yyyy-mm-dd') from dual;
判断日期在这个月
PLAN_DATE between to_char(trunc(sysdate, 'mm'),'yyyy-mm-dd') and to_char(last_day(trunc(sysdate)),'yyyy-mm-dd')
判断日期在下月
PLAN_DATE between to_char(last_day(SYSDATE) + 1,'yyyy-mm-dd') and to_char(last_day(add_months(trunc(sysdate),1)),'yyyy-mm-dd')