oracle中to_date详细用法示例(oracle日期格式转换)--688IT编程网

oracle中to_date详细⽤法⽰例（oracle⽇期格式转换）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

2. 字符串和时间互转

select to_date('2004-05-07 13:23:44','yyyy-mm-dd hh24:mi:ss') from dual

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.查询特殊条件天数

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)

select months_between(to_date('01-31-1999','MM-DD-YYYY'),

to_date('12-31-1998','MM-DD-YYYY')) "MONTHS" FROM DUAL;

//结果为：1

select months_between(to_date('02-01-1999','MM-DD-YYYY'),

to_date('12-31-1998','MM-DD-YYYY')) "MONTHS" FROM DUAL;

/结果为：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.获得⼩时数

//extract()出⽇期或间隔值的字段值

SELECT EXTRACT(HOUR FROM TIMESTAMP '2001-02-16 2:38:40') from offer select sysdate ,to_char(sysdate,'hh') from dual;

SYSDATE TO_CHAR(SYSDATE,'HH')

-------------------- ---------------------

2003-10-13 19:35:21 07

select sysdate ,to_char(sysdate,'hh24') from dual;

SYSDATE TO_CHAR(SYSDATE,'HH24')

-------------------- -----------------------

2003-10-13 19:35:21 19

12.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)

) MONTHS,

newer_date,

older_date

FROM

(

SELECT

hiredate older_date,

ADD_MONTHS (hiredate, ROWNUM) + ROWNUM newer_date

FROM

)

13.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 14.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

<与rrrr的区别

YYYY99 TO_C

------- ----

yyyy 99 0099

rrrr 99 1999

yyyy 01 0001

rrrr 01 2001

16.不同时区的处理

select to_char( NEW_TIME( sysdate, 'GMT','EST'), 'dd/mm/yyyy hh:mi:ss') ,

sysdate from dual;

17. 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

18.⼀年的第⼏天

select TO_CHAR(SYSDATE,'DDD'),sysdate from dual

//310 2002-11-6 10:03:51

19.计算⼩时，分，秒，毫秒

SELECT

Days,

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.

<_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 dual //⽇期返回的是天然后转换为ss

21,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

22,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

23，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

24.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