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小時(shí)格式下時(shí)間范圍為： 0:00:00 - 23:59:59....
12小時(shí)格式下時(shí)間范圍為： 1:00:00 - 12:59:59 ....
1.
日期和字符轉(zhuǎn)換函數(shù)用法（to_date,to_char）
2.
select to_char( to_date(222,'J'),'Jsp') from dual
顯示Two Hundred Twenty-Two
3.
求某天是星期幾
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
設(shè)置日期語(yǔ)言
Alter SESSION SET NLS_DATE_LANGUAGE='AMERICAN';
也可以這樣
TO_DATE ('2002-08-26', 'YYYY-mm-dd', 'NLS_DATE_LANGUAGE = American')
4.
兩個(gè)日期間的天數(shù)
select floor(sysdate - to_date('20020405','yyyymmdd')) from dual;
5. 時(shí)間為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號(hào)中午12點(diǎn)之后和12月1號(hào)的12點(diǎn)之前是不包含在這個(gè)范圍之內(nèi)的。
所以，當(dāng)時(shí)間需要精確的時(shí)候，覺得to_char還是必要的
7. 日期格式?jīng)_突問題
輸入的格式要看你安裝的ORACLE字符集的類型, 比如: US7ASCII, date格式的類型就是: '01-Jan-01'
alter system set NLS_DATE_LANGUAGE = American
alter session set NLS_DATE_LANGUAGE = American
或者在to_date中寫
select to_char(to_date('2002-08-26','yyyy-mm-dd'),'day','NLS_DATE_LANGUAGE = American') from dual;
注意我這只是舉了NLS_DATE_LANGUAGE，當(dāng)然還有很多，
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間除星期一和七的天數(shù)
在前后分別調(diào)用DBMS_UTILITY.GET_TIME, 讓后將結(jié)果相減(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：第一條記錄的TIME 與最后一行是一樣的
可以建立一個(gè)函數(shù)來(lái)處理這個(gè)問題
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.
獲得小時(shí)數(shù)
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
獲取年月日與此類似
13.
年月日的處理
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.
處理月份天數(shù)不定的辦法
select to_char(add_months(last_day(sysdate) +1, -2), 'yyyymmdd'),last_day(sysdate) from dual
16.
找出今年的天數(shù)
select add_months(trunc(sysdate,'year'), 12) - trunc(sysdate,'year') from dual
閏年的處理方法
to_char( last_day( to_date('02' || :year,'mmyyyy') ), 'dd' )
如果是28就不是閏年
17.
yyyy與rrrr的區(qū)別
'YYYY99 TO_C
------- ----
yyyy 99 0099
rrrr 99 1999
yyyy 01 0001
rrrr 01 2001
18.不同時(shí)區(qū)的處理
select to_char( NEW_TIME( sysdate, 'GMT','EST'), 'dd/mm/yyyy hh:mi:ss') ,sysdate
from dual;
19.
5秒鐘一個(gè)間隔
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位秒數(shù)
20.
一年的第幾天
select TO_CHAR(SYSDATE,'DDD'),sysdate from dual
310 2002-11-6 10:03:51
21.計(jì)算小時(shí),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) 作為年
floor((date2-date1, 365) /30) 作為月
mod(mod(date2-date1, 365), 30)作為日.
23.next_day函數(shù)
next_day(sysdate,6)是從當(dāng)前開始下一個(gè)星期五。后面的數(shù)字是從星期日開始算起。