select trunc(sysdate) from dual --当天
select to_date(to_char(sysdate,'yyyy-MM')||'01','yyyy-MM-dd') from dual--当月的第一天
select to_char(trunc(sysdate, 'mm'),'yyyy-MM-dd') from dual --当月第一天
select to_char(trunc(add_months(last_day(sysdate), -1) + 1), 'yyyy-mm-dd') from dual--当月第一天
--月份列表
SELECT TO_CHAR(ADD_MONTHS(TO_DATE('2014-10', 'yyyy-MM'), ROWNUM - 1), 'yyyy-MM') as monthlist
FROM DUAL
CONNECT BY ROWNUM <= months_between(to_date('2015-06', 'yyyy-MM'), to_date('2014-10', 'yyyy-MM')) + 1
--日期列表
SELECT to_char(to_date('2018-01-01','yyyy-mm-dd')+rownum-1,'yyyy-mm-dd') ymd1
FROM DUAL CONNECT BY rownum<= (to_date('2018-12-31','yyyy-mm-dd')-to_date('2018-01-01','yyyy-mm-dd')+1)