SQL自動產生多個日期

select sysdate-lvl
  from dual a,
           (
             select level lvl from dual connect by level <= 3
           ) b;

--上月21號到今天有幾天
select sysdate-lvl
          from dual a,(select level lvl from dual connect by level <= trunc(sysdate)-(trunc(add_months(sysdate,-1),'mm')+20)) b