select   sysdate,to_char(sysdate,'D')   from   dual;   

2017/1/4 14:08:00        4

select   to_char(sysdate,'yyyy')   from   dual;   --年
select   to_char(sysdate,'Q'   from   dual;           --季
select   to_char(sysdate,'mm')   from   dual;       --月
select   to_char(sysdate,'dd')   from   dual;       --日
ddd   年中的第几天
WW   年中的第几个星期
W   该月中第几个星期
D   周中的星期几
hh   小时(12)
hh24   小时(24)
Mi   分
ss   秒

 select   to_char(sysdate,'day')   from   dual;   输出结果：星期三

select sysdate from dual;
输出结果：2017/1/4 14:11:17

select trunc(sysdate) from dual;
输出结果：2017/1/4

select trunc(sysdate) + 0.99999 from dual;
输出结果：2017/1/4 23:59:59

select trunc(sysdate) + 1/24 from dual;select trunc(sysdate) + 7/24 from dual;

select trunc(sysdate+1) from dual;select trunc(sysdate)+1 from dual;

select trunc(sysdate,'mm') from dual;
输出结果：2017/1/1

select trunc(add_months(sysdate,1),'mm') from dual;
输出结果：2017/2/1

select last_day(sysdate)  from dual;
select last_day(trunc(sysdate))  from dual;
select trunc(last_day(sysdate))  from dual;
select trunc(add_months(sysdate,1),'mm') - 1 from dual;//下个月一号减一天

select trunc(sysdate,'yyyy')+ rn -1 date0
from
(select rownum rn from all_objects
where rownum<366);

select trunc(sysdate,'mm')+rn*7-7 from
(
select rownum rn from all_objects
where rownum<7
)

select trunc(sysdate,'d')-6+rn*7 from
(
select rownum rn from all_objects
where rownum<7
)

SELECT TO_CHAR(SYSDATE,'DDD') FROM DUAL;

select add_months(sysdate,24) from dual;

select decode(to_char(last_day(trunc(sysdate,'y')+31),'dd'),'29','闰年','平年') from dual;

select decode(to_char(last_day(trunc(add_months(sysdate,24),'y')+31),'dd'),'29','闰年','平年') from dual;

select ceil(to_number(to_char(sysdate,'mm'))/3) from dual;select to_char(sysdate, 'Q') from dual;