oracle 日期/时间函数

摘自他出，只为学习。

 

 

 

　Oracle关于时间/日期的操作

　　1.日期时间间隔操作

　　当前时间减去7分钟的时间

　　

select sysdate,sysdate - interval '7' MINUTE from dual

select sysdate,sysdate - interval '7' MINUTE from dual

　　当前时间减去7小时的时间

　　

select sysdate - interval '7' hour from dual

select sysdate - interval '7' hour from dual

　　当前时间减去7天的时间

　　

select sysdate - interval '7' day from dual

select sysdate - interval '7' day from dual

　　当前时间减去7月的时间

　　

select sysdate,sysdate - interval '7' month from dual

select sysdate,sysdate - interval '7' month from dual

　　当前时间减去7年的时间

　　

select sysdate,sysdate - interval '7' year from dual

select sysdate,sysdate - interval '7' year from dual

　　时间间隔乘以一个数字

　　

select sysdate,sysdate - 8 *interval '2' hour from dual

select sysdate,sysdate - 8 *interval '2' hour from dual

　　2.日期到字符操作

　　select sysdate,to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') from dual

　　select sysdate,to_char(sysdate,'yyyy-mm-dd hh:mi:ss') from dual

　　select sysdate,to_char(sysdate,'yyyy-ddd hh:mi:ss') from dual

　　select sysdate,to_char(sysdate,'yyyy-mm iw-d hh:mi:ss') from dual

　　select sysdate,to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') from dual

　　select sysdate,to_char(sysdate,'yyyy-mm-dd hh:mi:ss') from dual

　　select sysdate,to_char(sysdate,'yyyy-ddd hh:mi:ss') from dual

　　select sysdate,to_char(sysdate,'yyyy-mm iw-d hh:mi:ss') from dual

　　参考oracle的相关关文档(ORACLE901DOC/SERVER.901/A90125/SQL_ELEMENTS4.HTM#48515)

　　3. 字符到日期操作

　　select to_date('2003-10-17 21:15:37','yyyy-mm-dd hh24:mi:ss') from dual

　　select to_date('2003-10-17 21:15:37','yyyy-mm-dd hh24:mi:ss') from dual

　　具体用法和上面的to_char差不多。

　　4. trunk/ ROUND函数的使用

　　select trunc(sysdate ,'YEAR') from dual

　　select trunc(sysdate ) from dual

　　select to_char(trunc(sysdate ,'YYYY'),'YYYY') from dual

　　select trunc(sysdate ,'YEAR') from dual

　　select trunc(sysdate ) from dual

　　select to_char(trunc(sysdate ,'YYYY'),'YYYY') from dual

　　5.oracle有毫秒级的数据类型

　　--返回当前时间 年月日小时分秒毫秒

　　select to_char(current_timestamp(5),'DD-MON-YYYY HH24:MI:SSxFF') from dual;

　　select to_char(current_timestamp(5),'DD-MON-YYYY HH24:MI:SSxFF') from dual;

　　--返回当前 时间的秒毫秒，可以指定秒后面的精度(最大=9)

　　

select to_char(current_timestamp(9),'MI:SSxFF') from dual;

select to_char(current_timestamp(9),'MI:SSxFF') from dual;

　　6.计算程序运行的时间(ms)

　　declare

　　type rc is ref cursor;

　　l_rc rc;

　　l_dummy all_objects.object_name%type;

　　l_start number default dbms_utility.get_time;

　　begin

　　for I in 1 .. 1000

　　loop

　　open l_rc for

　　'select object_name from all_objects '||

　　'where object_id = ' || i;

　　fetch l_rc into l_dummy;

　　close l_rc;

　　end loop;

　　dbms_output.put_line

　　( round( (dbms_utility.get_time-l_start)/100, 2 ) ||

　　' seconds...' );

　　end;

　　declare

　　type rc is ref cursor;

　　l_rc rc;

　　l_dummy all_objects.object_name%type;

　　l_start number default dbms_utility.get_time;

　　begin

　　for I in 1 .. 1000

　　loop

　　open l_rc for

　　'select object_name from all_objects '||

　　'where object_id = ' || i;

　　fetch l_rc into l_dummy;

　　close l_rc;

　　end loop;

　　dbms_output.put_line

　　( round( (dbms_utility.get_time-l_start)/100, 2 ) ||

　　' seconds...' );

　　end;

7、add_months()用于从一个日期值增加或减少一些月份





1〉获得若干分钟前的时间

select sysdate,sysdate - N/(60*24) from dual;

select sysdate,sysdate - N/(60*24) from dual;

或者

select sysdate,sysdate - interval 'N' minute from dual

select sysdate,sysdate - interval 'N' minute from dual

2〉获得若干分钟后的时间 s

elect sysdate,sysdate + N/(60*24) from dual;

elect sysdate,sysdate + N/(60*24) from dual;

或者

select sysdate,sysdate + interval 'N' minute from dual

select sysdate,sysdate + interval 'N' minute from dual

注释："N"表示需要减去或者加上的分钟数

3〉获得若干秒前的时间 s

elect sysdate,sysdate - N*0.00001 from dual;

elect sysdate,sysdate - N*0.00001 from dual;

或者

select sysdate,sysdate - N/(60*60*24) from dual;

select sysdate,sysdate - N/(60*60*24) from dual;

或者

select sysdate,sysdate - interval 'N' second from dual

select sysdate,sysdate - interval 'N' second from dual 

4〉获得若干秒后的时间

select sysdate,sysdate + N*0.00001 from dual;

select sysdate,sysdate + N*0.00001 from dual;

或者

select sysdate,sysdate - N/(60*60*24) from dual;

select sysdate,sysdate - N/(60*60*24) from dual;

或者

select sysdate,sysdate + interval 'N' second from dual

select sysdate,sysdate + interval 'N' second from dual

注释："N"表示需要减去或者加上的秒数
注释：N*0.00001 等价于 N/(60*60*24)

5〉获得若干小时前的时间

select sysdate,sysdate - N*/24 from dual;

select sysdate,sysdate - N*/24 from dual;

或者

select sysdate,sysdate - interval 'N' hour from dual

select sysdate,sysdate - interval 'N' hour from dual

6〉获得若干小时后的时间

select sysdate,sysdate + N*/24 from dual;

 select sysdate,sysdate + N*/24 from dual;

或者

select sysdate,sysdate + interval 'N' hour from dual

select sysdate,sysdate + interval 'N' hour from dual

注释："N"表示需要减去或者加上的小时数

7〉获得若干月之后同一时间

select sysdate,add_months(sysdate,N) from dual;

select sysdate,add_months(sysdate,N) from dual;

或者

select sysdate,sysdate + interval 'N' month from dual

select sysdate,sysdate + interval 'N' month from dual

8〉获得若干月之前的同一时间

select sysdate,add_months(sysdate,-N) from dual;

select sysdate,add_months(sysdate,-N) from dual;

或者

select sysdate,sysdate - interval 'N' month from dual

select sysdate,sysdate - interval 'N' month from dual

注释："N"表示需要减去或者加上的月数

9〉获得某个日期所在月份的第一天

select sysdate,trunc(sysdate,'mm') from dual;

select sysdate,trunc(sysdate,'mm') from dual;

10〉获得某个日期所在年的第一天

select sysdate,trunc(sysdate,'yyyy') from dual;

select sysdate,trunc(sysdate,'yyyy') from dual;

或者

select sysdate,to_date(to_char((to_number(to_char(sysdate,'yyyy')) * 100 + 1) * 100 + 1),'yyyymmdd') from dual

select sysdate,to_date(to_char((to_number(to_char(sysdate,'yyyy')) * 100 + 1) * 100 + 1),'yyyymmdd') from dual

11〉获得某个日期所在年的最后一天

select sysdate,to_date((to_char(sysdate,'yyyy') || '1231'),'yyyymmdd') from dual;

select sysdate,to_date((to_char(sysdate,'yyyy') || '1231'),'yyyymmdd') from dual;

或者

select sysdate,to_date(to_char((to_number(to_char(sysdate,'yyyy'))* 100 + 12) * 100 + 31),'yyyymmdd') from dual

select sysdate,to_date(to_char((to_number(to_char(sysdate,'yyyy'))* 100 + 12) * 100 + 31),'yyyymmdd') from dual

12〉获得某个日期所在月份的最后一天

select sysdate,last_day(sysdate) from dual;

select sysdate,last_day(sysdate) from dual;

13〉获得两个日期之间的时数

select t.intime,t.outtime,trunc(24*(t.outtime-t.intime)) from hr_carding t

select t.intime,t.outtime,trunc(24*(t.outtime-t.intime)) from hr_carding t

14〉获得两个日期之间的天数

select t.begintime,t.endtime,trunc(t.endtime-t.begintime) from hr_absence t

select t.begintime,t.endtime,trunc(t.endtime-t.begintime) from hr_absence t

15〉获得若干天前的时间 s

elect sysdate,sysdate - N from dual;

elect sysdate,sysdate - N from dual;

或者

select sysdate,sysdate - interval 'N' day from dual

select sysdate,sysdate - interval 'N' day from dual

16〉获得若干天后的时间

select sysdate,sysdate + N from dual;

select sysdate,sysdate + N from dual;

或者

select sysdate,sysdate + interval 'N' day from dual

select sysdate,sysdate + interval 'N' day from dual

注释："N"表示需要减去或者加上的天数

17〉获得若干年前的时间

select sysdate,add_months(sysdate,-12*N) from dual;

select sysdate,add_months(sysdate,-12*N) from dual;

或者

select sysdate,sysdate - interval 'N' year from dual

select sysdate,sysdate - interval 'N' year from dual

16〉获得若干年后的时间

select sysdate,add_months(sysdate,12*N) from dual;

select sysdate,add_months(sysdate,12*N) from dual;

或者

select sysdate,sysdate + interval 'N' year from dual

select sysdate,sysdate + interval 'N' year from dual

注释："N"表示需要减去或者加上的年数

17〉相隔若干小时的时间

select sysdate,sysdate - M * interval 'N' hour from dual

select sysdate,sysdate - M * interval 'N' hour from dual 

18〉检索出某一个日期所在月份的所有天信息

select trunc(to_date('X','yyyymmdd'),'mm') from dual
union all
select trunc(to_date('X','yyyymmdd'),'mm') + rownum from dual
connect by rownum <= (last_day(to_date('X','yyyymmdd')) - trunc(to_date('X','yyyymmdd'),'mm'))

select trunc(to_date('X','yyyymmdd'),'mm') from dual
union all
select trunc(to_date('X','yyyymmdd'),'mm') + rownum from dual
connect by rownum <= (last_day(to_date('X','yyyymmdd')) - trunc(to_date('X','yyyymmdd'),'mm'))

或者

select first + rownum - 1 myday
from (select trunc(to_date('X','yyyymmdd'),'MM') first,trunc(last_day(to_date('X','yyyymmdd'))) last from dual)
connect by rownum <= last - first + 1

select first + rownum - 1 myday
from (select trunc(to_date('X','yyyymmdd'),'MM') first,trunc(last_day(to_date('X','yyyymmdd'))) last from dual)
connect by rownum <= last - first + 1

其中：字符串'X'表示某一个日期

19〉怎样知道今天是星期几

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

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

在获取之前可以设置日期语言,如:

ALTER SESSION SET NLS_DATE_LANGUAGE='AMERICAN';

ALTER SESSION SET NLS_DATE_LANGUAGE='AMERICAN';

还可以在函数中指定

select to_char(to_date('2002-08-26','yyyy-mm-dd'),'day','NLS_DATE_LANGUAGE = AMERICAN') from dual;

select to_char(to_date('2002-08-26','yyyy-mm-dd'),'day','NLS_DATE_LANGUAGE = AMERICAN') from dual; 

其它更多用法,可以参考to_char与to_date函数

20〉本月的天数

SELECT to_char(last_day(SYSDATE),'dd') days FROM dual

SELECT to_char(last_day(SYSDATE),'dd') days FROM dual

21〉今年的天数

select add_months(trunc(sysdate, 'year'), 12) - trunc(sysdate, 'year') /*下一年的第一天减去今年的第一天*/
from dual

select add_months(trunc(sysdate, 'year'), 12) - trunc(sysdate, 'year') /*下一年的第一天减去今年的第一天*/
from dual

22〉下个星期一的日期

SELECT Next_day(SYSDATE,'monday') FROM dual

SELECT Next_day(SYSDATE,'monday') FROM dual

23〉怎么样从数据库中获得毫秒
9i以上版本，有一个timestamp类型获得毫秒，如

select to_char(systimestamp ,'yyyy-mm-dd hh24:mi:ssxff') time1,
to_char(current_timestamp,'yyyy-mm-dd hh24:mi:ssxff') time2
from dual;

select to_char(systimestamp ,'yyyy-mm-dd hh24:mi:ssxff') time1, 
to_char(current_timestamp,'yyyy-mm-dd hh24:mi:ssxff') time2 
from dual;

24〉检索某一年度的日历表：

select case
when (new_yweek = min(new_yweek)
over(partition by mon order by new_yweek)) then
mon
else
null
end as mon,
new_yweek as yweek,
row_number() over(partition by mon order by new_yweek) as mweek,
sum(decode(wday, '1', mday, null)) as sunday,
sum(decode(wday, '2', mday, null)) as monday,
sum(decode(wday, '3', mday, null)) as tuesday,
sum(decode(wday, '4', mday, null)) as wednesday,
sum(decode(wday, '5', mday, null)) as thursday,
sum(decode(wday, '6', mday, null)) as friday,
sum(decode(wday, '7', mday, null)) as saturday,
&year as year
from (select to_date(&year || '0101', 'yyyymmdd') + rownum - 1 as everyday,
to_char(to_date(&year || '0101', 'yyyymmdd') + rownum - 1,
'mm') as mon,
to_char(to_date(&year || '0101', 'yyyymmdd') + rownum - 1,
'w') as mweek,
to_char(to_date(&year || '0101', 'yyyymmdd') + rownum - 1,
'ww') as yweek,
case
when (to_char(to_date(&year || '0101', 'yyyymmdd'), 'd') > '1') and
(to_char(to_date(&year || '0101', 'yyyymmdd') + rownum - 1,
'd') <
to_char(to_date(&year || '0101', 'yyyymmdd'), 'd')) then
to_char(to_char(to_date(&year || '0101', 'yyyymmdd') +
rownum - 1,
'ww') + 1,
'fm00')
else
to_char(to_date(&year || '0101', 'yyyymmdd') + rownum - 1,
'ww')
end as new_yweek,
to_char(to_date(&year || '0101', 'yyyymmdd') + rownum - 1,
'd') as wday,
to_char(to_date(&year || '0101', 'yyyymmdd') + rownum - 1,
'dd') as mday
from (select rownum r from dual connect by rownum <= 366)
where rownum <=
to_char(to_date(&year || '1231', 'yyyymmdd'), 'ddd'))
group by mon, new_yweek

select case
when (new_yweek = min(new_yweek)
over(partition by mon order by new_yweek)) then
mon
else
null
end as mon,
new_yweek as yweek,
row_number() over(partition by mon order by new_yweek) as mweek,
sum(decode(wday, '1', mday, null)) as sunday,
sum(decode(wday, '2', mday, null)) as monday,
sum(decode(wday, '3', mday, null)) as tuesday,
sum(decode(wday, '4', mday, null)) as wednesday,
sum(decode(wday, '5', mday, null)) as thursday,
sum(decode(wday, '6', mday, null)) as friday,
sum(decode(wday, '7', mday, null)) as saturday,
&year as year
from (select to_date(&year || '0101', 'yyyymmdd') + rownum - 1 as everyday,
to_char(to_date(&year || '0101', 'yyyymmdd') + rownum - 1,
'mm') as mon,
to_char(to_date(&year || '0101', 'yyyymmdd') + rownum - 1,
'w') as mweek,
to_char(to_date(&year || '0101', 'yyyymmdd') + rownum - 1,
'ww') as yweek,
case
when (to_char(to_date(&year || '0101', 'yyyymmdd'), 'd') > '1') and
(to_char(to_date(&year || '0101', 'yyyymmdd') + rownum - 1,
'd') <
to_char(to_date(&year || '0101', 'yyyymmdd'), 'd')) then
to_char(to_char(to_date(&year || '0101', 'yyyymmdd') +
rownum - 1,
'ww') + 1,
'fm00')
else
to_char(to_date(&year || '0101', 'yyyymmdd') + rownum - 1,
'ww')
end as new_yweek,
to_char(to_date(&year || '0101', 'yyyymmdd') + rownum - 1,
'd') as wday,
to_char(to_date(&year || '0101', 'yyyymmdd') + rownum - 1,
'dd') as mday
from (select rownum r from dual connect by rownum <= 366)
where rownum <=
to_char(to_date(&year || '1231', 'yyyymmdd'), 'ddd'))
group by mon, new_yweek