Oracle时间日期函数
TO_DATE格式(以时间:2007-11-02?? 13:45:25为例)
Year:?????
yy two digits 两位年??????????????? 显示值:07
yyy three digits 三位年??????????????? 显示值:007
yyyy four digits 四位年??????????????? 显示值:2007
Month:?????
mm??? number???? 两位月????????????? 显示值:11
mon??? abbreviated 字符集表示????????? 显示值:11月,若是英文版,显示nov????
month spelled out 字符集表示????????? 显示值:11月,若是英文版,显示november
Day:?????
dd??? number???????? 当月第几天??????? 显示值:02
ddd??? number???????? 当年第几天??????? 显示值:02
dy??? abbreviated 当周第几天简写??? 显示值:星期五,若是英文版,显示fri
day??? spelled out?? 当周第几天全写??? 显示值:星期五,若是英文版,显示friday???????
ddspth spelled out, ordinal twelfth
Hour:
hh??? two digits 12小时进制??????????? 显示值:01
hh24 two digits 24小时进制??????????? 显示值:13
Minute:
mi??? two digits 60进制??????????????? 显示值:45
Second:
ss??? two digits 60进制??????????????? 显示值:25
其它
Q???? digit???????? 季度????????????????? 显示值:4
WW??? digit???????? 当年第几周??????????? 显示值:44
W??? digit????????? 当月第几周??????????? 显示值:1
24小时格式下时间范围为： 0:00:00 - 23:59:59....?????
12小时格式下时间范围为： 1:00:00 - 12:59:59 ....
1. 日期和字符转换函数用法（to_date,to_char）
select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') as nowTime from dual;?? //日期转化为字符串??
select to_char(sysdate,'yyyy') as nowYear?? from dual;?? //获取时间的年??
select to_char(sysdate,'mm')??? as nowMonth from dual;?? //获取时间的月??
select to_char(sysdate,'dd')??? as nowDay??? from dual;?? //获取时间的日??
select to_char(sysdate,'hh24') as nowHour?? from dual;?? //获取时间的时??
select to_char(sysdate,'mi')??? as nowMinute from dual;?? //获取时间的分??
select to_char(sysdate,'ss')??? as nowSecond from dual;?? //获取时间的秒
???
select to_date('2004-05-07 13:23:44','yyyy-mm-dd hh24:mi:ss')??? from dual//
2.?????
select to_char( to_date(222,'J'),'Jsp') from dual?????
显示Two Hundred Twenty-Two????
3.求某天是星期几?????
select to_char(to_date('2002-08-26','yyyy-mm-dd'),'day') from dual;?????
星期一?????
select to_char(to_date('2002-08-26','yyyy-mm-dd'),'day','NLS_DATE_LANGUAGE = American') from dual;?????
monday?????
设置日期语言?????
ALTER SESSION SET NLS_DATE_LANGUAGE='AMERICAN';?????
也可以这样?????
TO_DATE ('2002-08-26', 'YYYY-mm-dd', 'NLS_DATE_LANGUAGE = American')????
4. 两个日期间的天数?????
select floor(sysdate - to_date('20020405','yyyymmdd')) from dual;????
5. 时间为null的用法?????
select id, active_date from table1?????
UNION?????
select 1, TO_DATE(null) from dual;?????
注意要用TO_DATE(null)????
6.月份差??
a_date between to_date('20011201','yyyymmdd') and to_date('20011231','yyyymmdd')?????
那么12月31号中午12点之后和12月1号的12点之前是不包含在这个范围之内的。?????
所以，当时间需要精确的时候，觉得to_char还是必要的
7. 日期格式冲突问题?????
输入的格式要看你安装的ORACLE字符集的类型, 比如: US7ASCII, date格式的类型就是: '01-Jan-01'?????
alter system set NLS_DATE_LANGUAGE = American?????
alter session set NLS_DATE_LANGUAGE = American?????
或者在to_date中写?????
select to_char(to_date('2002-08-26','yyyy-mm-dd'),'day','NLS_DATE_LANGUAGE = American') from dual;?????
注意我这只是举了NLS_DATE_LANGUAGE，当然还有很多，?????
可查看?????
select * from nls_session_parameters?????
select * from V$NLS_PARAMETERS????
8.?????
select count(*)?????
from ( select rownum-1 rnum?????
from all_objects?????
where rownum <= to_date('2002-02-28','yyyy-mm-dd') - to_date('2002-?????
02-01','yyyy-mm-dd')+1?????
)?????
where to_char( to_date('2002-02-01','yyyy-mm-dd')+rnum-1, 'D' )?????
not in ( '1', '7' )?????
查找2002-02-28至2002-02-01间除星期一和七的天数?????
在前后分别调用DBMS_UTILITY.GET_TIME, 让后将结果相减(得到的是1/100秒, 而不是毫秒).????
9. 查找月份????
select months_between(to_date('01-31-1999','MM-DD-YYYY'),to_date('12-31-1998','MM-DD-YYYY')) "MONTHS" FROM DUAL;?????
1?????
select months_between(to_date('02-01-1999','MM-DD-YYYY'),to_date('12-31-1998','MM-DD-YYYY')) "MONTHS" FROM DUAL;?????
1.03225806451613
10. Next_day的用法?????
Next_day(date, day)?????
Monday-Sunday, for format code DAY?????
Mon-Sun, for format code DY?????
1-7, for format code D????
11?????
select to_char(sysdate,'hh:mi:ss') TIME from all_objects?????
注意：第一条记录的TIME 与最后一行是一样的?????
可以建立一个函数来处理这个问题?????
create or replace function sys_date return date is?????
begin?????
return sysdate;?????
end;?????
select to_char(sys_date,'hh:mi:ss') from all_objects;??
12.获得小时数?????
extract()找出日期或间隔值的字段值
SELECT EXTRACT(HOUR FROM TIMESTAMP '2001-02-16 2:38:40') from offer?????
SQL> select sysdate ,to_char(sysdate,'hh') from dual;?????
SYSDATE TO_CHAR(SYSDATE,'HH')?????
-------------------- ---------------------?????
2003-10-13 19:35:21 07?????
SQL> select sysdate ,to_char(sysdate,'hh24') from dual;?????
SYSDATE TO_CHAR(SYSDATE,'HH24')?????
-------------------- -----------------------?????
2003-10-13 19:35:21 19????
??????
13.年月日的处理?????
select older_date,?????
newer_date,?????
years,?????
months,?????
abs(?????
trunc(?????
newer_date-?????
add_months( older_date,years*12+months )?????
)?????
) days
from ( select?????
trunc(months_between( newer_date, older_date )/12) YEARS,?????
mod(trunc(months_between( newer_date, older_date )),12 ) MONTHS,?????
newer_date,?????
older_date?????
from (
select hiredate older_date, add_months(hiredate,rownum)+rownum newer_date?????
from emp
)?????
)????
14.处理月份天数不定的办法?????
select to_char(add_months(last_day(sysdate) +1, -2), 'yyyymmdd'),last_day(sysdate) from dual????
16.找出今年的天数?????
select add_months(trunc(sysdate,'year'), 12) - trunc(sysdate,'year') from dual????
?? 闰年的处理方法?????
to_char( last_day( to_date('02'??? | | :year,'mmyyyy') ), 'dd' )?????
如果是28就不是闰年????
17.yyyy与rrrr的区别?????
'YYYY99 TO_C?????
------- ----?????
yyyy 99 0099?????
rrrr 99 1999?????
yyyy 01 0001?????
rrrr 01 2001????
18.不同时区的处理?????
select to_char( NEW_TIME( sysdate, 'GMT','EST'), 'dd/mm/yyyy hh:mi:ss') ,sysdate?????
from dual;????
19.5秒钟一个间隔?????
Select TO_DATE(FLOOR(TO_CHAR(sysdate,'SSSSS')/300) * 300,'SSSSS') ,TO_CHAR(sysdate,'SSSSS')?????
from dual????
?? 2002-11-1 9:55:00 35786?????
SSSSS表示5位秒数????
20.一年的第几天?????
select TO_CHAR(SYSDATE,'DDD'),sysdate from dual
310 2002-11-6 10:03:51????
21.计算小时,分,秒,毫秒?????
select?????
Days,?????
A,?????
TRUNC(A*24) Hours,?????
TRUNC(A*24*60 - 60*TRUNC(A*24)) Minutes,?????
TRUNC(A*24*60*60 - 60*TRUNC(A*24*60)) Seconds,?????
TRUNC(A*24*60*60*100 - 100*TRUNC(A*24*60*60)) mSeconds?????
from?????
(?????
select?????
trunc(sysdate) Days,?????
sysdate - trunc(sysdate) A?????
from dual?????
)????
?? select * from tabname?????
order by decode(mode,'FIFO',1,-1)*to_char(rq,'yyyymmddhh24miss');?????
//?????
floor((date2-date1) /365) 作为年?????
floor((date2-date1, 365) /30) 作为月?????
d(mod(date2-date1, 365), 30)作为日.
23.next_day函数????? 返回下个星期的日期,day为1-7或星期日-星期六,1表示星期日
next_day(sysdate,6)是从当前开始下一个星期五。后面的数字是从星期日开始算起。?????
1 2 3 4 5 6 7?????
日 一 二 三 四 五 六???
---------------------------
select??? (sysdate-to_date('2003-12-03 12:55:45','yyyy-mm-dd hh24:mi:ss'))*24*60*60 from ddual
日期 返回的是天 然后 转换为ss
24,round[舍入到最接近的日期](day:舍入到最接近的星期日)
select sysdate S1,
round(sysdate) S2 ,
round(sysdate,'year') YEAR,
round(sysdate,'month') MONTH ,
round(sysdate,'day') DAY from dual
25,trunc[截断到最接近的日期,单位为天] ,返回的是日期类型
select sysdate S1,????????????????????
trunc(sysdate) S2,???????????????? //返回当前日期,无时分秒
trunc(sysdate,'year') YEAR,??????? //返回当前年的1月1日,无时分秒
trunc(sysdate,'month') MONTH ,???? //返回当前月的1日,无时分秒
trunc(sysdate,'day') DAY?????????? //返回当前星期的星期天,无时分秒
from dual
26,返回日期列表中最晚日期
select greatest('01-1月-04','04-1月-04','10-2月-04') from dual
27.计算时间差
注:oracle时间差是以天数为单位,所以换算成年月,日
select floor(to_number(sysdate-to_date('2007-11-02 15:55:03','yyyy-mm-dd hh24:mi:ss'))/365) as spanYears from dual??????? //时间差-年
select ceil(moths_between(sysdate-to_date('2007-11-02 15:55:03','yyyy-mm-dd hh24:mi:ss'))) as spanMonths from dual??????? //时间差-月
select floor(to_number(sysdate-to_date('2007-11-02 15:55:03','yyyy-mm-dd hh24:mi:ss'))) as spanDays from dual???????????? //时间差-天
select floor(to_number(sysdate-to_date('2007-11-02 15:55:03','yyyy-mm-dd hh24:mi:ss'))*24) as spanHours from dual???????? //时间差-时
select floor(to_number(sysdate-to_date('2007-11-02 15:55:03','yyyy-mm-dd hh24:mi:ss'))*24*60) as spanMinutes from dual??? //时间差-分
select floor(to_number(sysdate-to_date('2007-11-02 15:55:03','yyyy-mm-dd hh24:mi:ss'))*24*60*60) as spanSeconds from dual //时间差-秒
28.更新时间
注:oracle时间加减是以天数为单位,设改变量为n,所以换算成年月,日
select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss'),to_char(sysdate+n*365,'yyyy-mm-dd hh24:mi:ss') as newTime from dual??????? //改变时间-年
select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss'),add_months(sysdate,n) as newTime from dual???????????????????????????????? //改变时间-月
select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss'),to_char(sysdate+n,'yyyy-mm-dd hh24:mi:ss') as newTime from dual??????????? //改变时间-日
select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss'),to_char(sysdate+n/24,'yyyy-mm-dd hh24:mi:ss') as newTime from dual???????? //改变时间-时
select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss'),to_char(sysdate+n/24/60,'yyyy-mm-dd hh24:mi:ss') as newTime from dual????? //改变时间-分
select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss'),to_char(sysdate+n/24/60/60,'yyyy-mm-dd hh24:mi:ss') as newTime from dual?? //改变时间-秒
29.查找月的第一天,最后一天
SELECT Trunc(Trunc(SYSDATE, 'MONTH') - 1, 'MONTH') First_Day_Last_Month,
Trunc(SYSDATE, 'MONTH') - 1 / 86400 Last_Day_Last_Month,
Trunc(SYSDATE, 'MONTH') First_Day_Cur_Month,
LAST_DAY(Trunc(SYSDATE, 'MONTH')) + 1 - 1 / 86400 Last_Day_Cur_Month
FROM dual;
?
