select to_char(trunc(sysdate),'ddd') from dual;
--找出当前月份的周五的日期
select to_char(sysdate,'ddd') from dual group by to_char(sysdate,'yyyy');
select to_char(t.d, 'YY-MM-DD')
from (select trunc(sysdate, 'MM') + rownum - 1 as d
from dba_objects
where rownum < 32) t
where to_char(t.d, 'MM') = to_char(sysdate, 'MM')
--查询今年的所有天数
select A.* from (select trunc(sysdate, 'YYYY') + rownum - 1 as d
from dba_objects
where rownum < 367) A where A.d <= add_months(trunc(sysdate, 'yyyy'), 12) - 1
--查询本年的最后一天
select add_months(trunc(sysdate, 'yyyy'), 12) - 1 from dual;