Oracle时间日期操作方法小结

Oracle时间⽇期操作⽅法⼩结
sysdate+(5/24/60/60) 在系统时间基础上延迟5秒
sysdate+5/24/60 在系统时间基础上延迟5分钟
sysdate+5/24 在系统时间基础上延迟5⼩时
sysdate+5 在系统时间基础上延迟5天
add_months(sysdate,-5) 在系统时间基础上延迟5⽉
add_months(sysdate,-5*12) 在系统时间基础上延迟5年
上⽉末的⽇期：select last_day(add_months(sysdate, -1)) from dual;
本⽉的最后⼀秒：select trunc(add_months(sysdate,1),'MM') - 1/24/60/60 from dual
本周星期⼀的⽇期：select trunc(sysdate,'day')+1 from dual
年初⾄今的天数：select ceil(sysdate - trunc(sysdate, 'year')) from dual;
今天是今年的第⼏周 :select to_char(sysdate,'fmww') from dual
今天是本⽉的第⼏周:SELECT TO_CHAR(SYSDATE,'WW') - TO_CHAR(TRUNC(SYSDATE,'MM'),'WW') + 1 AS "weekOfMon" FROM dual
本⽉的天数
SELECT to_char(last_day(SYSDATE),'dd') days FROM dual
今年的天数
select add_months(trunc(sysdate,'year'), 12) - trunc(sysdate,'year') from dual
下个星期⼀的⽇期
SELECT Next_day(SYSDATE,'monday') FROM dual
＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝
--计算⼯作⽇⽅法
create table t(s date,e date);
alter session set nls_date_format = 'yyyy-mm-dd';
insert into t values('2003-03-01','2003-03-03');
insert into t values('2003-03-02','2003-03-03');
insert into t values('2003-03-07','2003-03-08');
insert into t values('2003-03-07','2003-03-09');
insert into t values('2003-03-05','2003-03-07');
insert into t values('2003-02-01','2003-03-31');
-- 这⾥假定⽇期都是不带时间的，否则在所有⽇期前加trunc即可。

select s,e,e-s+1 total_days,
trunc((e-s+1)/7)*5 + length(replace(substr('01111100111110',to_char(s,'d'),mod(e-s+1,7)),'0','')) work_days
from t;
-- drop table t;
引此：/showthread.php?
s=1635506cd5f48b1bc3adbe4cde96f227&threadid=104060&perpage=15&pagenumber=1
================================================================================
判断当前时间是上午下午还是晚上
SELECT CASE
WHEN to_number(to_char(SYSDATE,'hh24')) BETWEEN 6 AND 11 THEN '上午'
WHEN to_number(to_char(SYSDATE,'hh24')) BETWEEN 11 AND 17 THEN '下午'
END
FROM dual;
================================================================================
Oracle 中的⼀些处理⽇期
将数字转换为任意时间格式.如秒:需要转换为天/⼩时
SELECT to_char(floor(TRUNC(936000/(60*60))/24))||'天'||to_char(mod(TRUNC(936000/(60*60)),24))||'⼩时' FROM DUAL TO_DATE格式
Day:
dd number 12
dy abbreviated fri
day spelled out friday
ddspth spelled out, ordinal twelfth
Month:
mm number 03
mon abbreviated mar
month spelled out march
Year:
yy two digits 98
yyyy four digits 1998
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）
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.
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.
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
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')
-------------------- ---------------------
SQL> select sysdate ,to_char(sysdate,'hh24') from dual;
SYSDATE TO_CHAR(SYSDATE,'HH24')
-------------------- -----------------------
2003-10-13 19:35:21 19
获取年⽉⽇与此类似
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
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
mod(mod(date2-date1, 365), 30)作为⽇.
23.next_day函数
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 dual
⽇期返回的是天然后转换为ss
转此：/leadbbs/Announce/Announce.asp?BoardID=42&ID=1769
将数字转换为任意时间格式.如秒:需要转换为天/⼩时
SELECT to_char(floor(TRUNC(936000/(60*60))/24))||'天'||to_char(mod(TRUNC(936000/(60*60)),24))||'⼩时' FROM DUAL TO_DATE格式
Day:
dd number 12
dy abbreviated fri
day spelled out friday
ddspth spelled out, ordinal twelfth
Month:
mm number 03
mon abbreviated mar
month spelled out march
Year:
yyyy four digits 1998
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）
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.
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
9.
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
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
获取年⽉⽇与此类似
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,
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
)
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
mod(mod(date2-date1, 365), 30)作为⽇.
23.next_day函数
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 dual
⽇期返回的是天然后转换为ss
转此：/leadbbs/Announce/Announce.asp?BoardID=42&ID=1769
将数字转换为任意时间格式.如秒:需要转换为天/⼩时
SELECT to_char(floor(TRUNC(936000/(60*60))/24))||'天'||to_char(mod(TRUNC(936000/(60*60)),24))||'⼩时' FROM DUAL TO_DATE格式
Day:
dd number 12
dy abbreviated fri
day spelled out friday
ddspth spelled out, ordinal twelfth
Month:
mm number 03
mon abbreviated mar
month spelled out march
Year:
yy two digits 98
yyyy four digits 1998
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）
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
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.
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.
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
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
获取年⽉⽇与此类似
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
mod(mod(date2-date1, 365), 30)作为⽇.
23.next_day函数
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 dual
⽇期返回的是天然后转换为ss
转此：/leadbbs/Announce/Announce.asp?BoardID=42&ID=1769
将数字转换为任意时间格式.如秒:需要转换为天/⼩时
SELECT to_char(floor(TRUNC(936000/(60*60))/24))||'天'||to_char(mod(TRUNC(936000/(60*60)),24))||'⼩时' FROM DUAL TO_DATE格式
Day:
dd number 12
dy abbreviated fri
day spelled out friday
ddspth spelled out, ordinal twelfth
Month:
mm number 03
mon abbreviated mar
month spelled out march
Year:
yy two digits 98
yyyy four digits 1998
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）
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.
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.
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
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
获取年⽉⽇与此类似
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
mod(mod(date2-date1, 365), 30)作为⽇.
23.next_day函数
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 dual
⽇期返回的是天然后转换为ss
在oracle中有很多关于⽇期的函数，如:
1、add_months()⽤于从⼀个⽇期值增加或减少⼀些⽉份
date_value:=add_months(date_value,number_of_months)
例:
SQL> select add_months(sysdate,12) "Next Year" from dual;
Next Year
----------
13-11⽉-04
SQL> select add_months(sysdate,112) "Last Year" from dual;
Last Year
----------
13-3⽉ -13
SQL>
2、current_date()返回当前会放时区中的当前⽇期
date_value:=current_date
SQL> column sessiontimezone for a15
SQL> select sessiontimezone,current_date from dual;
SESSIONTIMEZONE CURRENT_DA
--------------- ----------
+08:00 13-11⽉-03
SQL> alter session set time_zone='-11:00'
2 /
会话已更改。

SQL> select sessiontimezone,current_timestamp from dual;
SESSIONTIMEZONE CURRENT_TIMESTAMP
--------------- ------------------------------------
-11:00 12-11⽉-03 04.59.13.668000 下午 -11:
00
SQL>
3、current_timestamp()以timestamp with time zone数据类型返回当前会放时区中的当前⽇期 timestamp_with_time_zone_value:=current_timestamp([timestamp_precision])
SQL> column sessiontimezone for a15
SQL> column current_timestamp format a36
SQL> select sessiontimezone,current_timestamp from dual;
SESSIONTIMEZONE CURRENT_TIMESTAMP
--------------- ------------------------------------
+08:00 13-11⽉-03 11.56.28.160000 上午 +08:
00
SQL> alter session set time_zone='-11:00'
2 /
会话已更改。

SQL> select sessiontimezone,current_timestamp from dual;
SESSIONTIMEZONE CURRENT_TIMESTAMP
--------------- ------------------------------------
-11:00 12-11⽉-03 04.58.00.243000 下午 -11:
00
SQL>
4、dbtimezone()返回时区
varchar_value:=dbtimezone
SQL> select dbtimezone from dual;
DBTIME
------
-07:00
SQL>
5、extract()找出⽇期或间隔值的字段值
date_value:=extract(date_field from [datetime_value|interval_value])
SQL> select extract(month from sysdate) "This Month" from dual;
This Month
----------
11
SQL> select extract(year from add_months(sysdate,36)) "3 Years Out" from dual;
3 Years Out
-----------
2006
SQL>
6、last_day()返回包含了⽇期参数的⽉份的最后⼀天的⽇期
date_value:=last_day(date_value)
SQL> select last_day(date'2000-02-01') "Leap Yr?" from dual;
Leap Yr?
----------
29-2⽉ -00
SQL> select last_day(sysdate) "Last day of this month" from dual;
Last day o
----------
30-11⽉-03
SQL>
7、localtimestamp()返回会话中的⽇期和时间
timestamp_value:=localtimestamp
SQL> column localtimestamp format a28
SQL> select localtimestamp from dual;
LOCALTIMESTAMP
----------------------------
13-11⽉-03 12.09.15.433000
下午
SQL> select localtimestamp,current_timestamp from dual;
LOCALTIMESTAMP CURRENT_TIMESTAMP
---------------------------- ------------------------------------
13-11⽉-03 12.09.31.006000 13-11⽉-03 12.09.31.006000 下午 +08:
下午 00
SQL> alter session set time_zone='-11:00';
会话已更改。

SQL> select localtimestamp,to_char(sysdate,'DD-MM-YYYY HH:MI:SS AM') "SYSDATE" from dual; LOCALTIMESTAMP SYSDATE
---------------------------- ------------------------
12-11⽉-03 05.11.31.259000 13-11-2003 12:11:31 下午
下午
SQL>
8、months_between()判断两个⽇期之间的⽉份数量。