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在Oracle中实现各种日期处理完全版


发布日期:2018年11月09日
 
在Oracle中实现各种日期处理完全版

TO_DATE格式

Day:

dd number

dy abbreviatedfri

dayspelled outfriday

ddspth spelled out ordinal twelfth

Month:

mm number

monabbreviatedmar

monthspelled outmarch

Year:

yy twodigits

yyyy fourdigits

小时格式下时间范围为 :: ::

小时格式下时间范围为 :: ::

日期和字符转换函数用法(to_dateto_char)

select to_char( to_date(J)Jsp)from dual

显示Two Hundred TwentyTwo

求某天是星期几

select to_char(to_date(yyyymmdd)day) from dual;

星期一

select to_char(to_date(yyyymmdd)dayNLS_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 ( YYYYmmdd NLS_DATE_LANGUAGE = American)

两个日期间的天数

select floor(sysdate to_date(yyyymmdd)) from dual;

时间为null的用法

select id active_date from table

UNION

select TO_DATE(null) from dual;

注意要用TO_DATE(null)

a_date between to_date(yyyymmdd) and to_date(yyyymmdd)

那么号中午点之后和号的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

日期格式沖突问题

输入的格式要看你安装的ORACLE字符集的类型 比如: USASCII date格式的类型就是: Jan

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(yyyymmdd)dayNLS_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

日期和字符转换函数用法(to_dateto_char)

We overwrite NLS_DATE_FORMAT into different formats for the session

SQL> alter session set nls_date_format = DDMONRR; Session altered

SQL> set pagesize

SQL> set linesize

SQL> select * from nls_session_parameters;

NLS_LANGUAGE AMERICAN

NLS_TERRITORYAMERICA

NLS_CURRENCY $

NLS_ISO_CURRENCY AMERICA

NLS_NUMERIC_CHARACTERS

NLS_CALENDAR GREGORIAN

NLS_DATE_FORMATDDMONRR

NLS_DATE_LANGUAGEAMERICAN

NLS_SORT BINARY

NLS_TIME_FORMATHHMISSXFF AM

NLS_TIMESTAMP_FORMAT DDMONRR HHMISSXFF AM

NLS_TIME_TZ_FORMAT HHMISSXFF AM TZH:TZM

NLS_TIMESTAMP_TZ_FORMATDDMONRR HHMISSXFF AM TZH:TZM

NLS_DUAL_CURRENCY$

NLS_COMP BINARY

rows selected

specify it in SQL statement:

SQL> select to_date(SEPDDMONYYYY) from dual;

SEP

SQL> alter session set nls_date_format = MMDDYYYY;

Session altered

SQL> select to_date(SEPDDMONYY) from dual;

TO_DATE(

SQL> alter session set nls_date_format = RRRRMMDD;

Session altered

SQL> select to_date(SEPDDMONYYYY) from dual;

TO_DATE(

When we use TO_CHAR function we get expected results of format fromcurrent SQL statement:

SQL> alter session set nls_date_format = MMDDYY;

Session altered

SQL> select to_char(sysdateddmmyyyy) from dual;

TO_CHAR(SYSDATEDDMMYYYY)

SQL> alter session set nls_date_format = RRMONDD;

Session altered

SQL> select to_char(sysdateddmonyy) from dual;

TO_CHAR(SYSDATEDDMONYY)

sep

SQL> select to_char(sysdateddMonyy) from dual;

TO_CHAR(SYSDATEDDMONYY)

Sep

select count(*)

from ( select rownum rnum

from all_objects

where rownum <= to_date(yyyymmdd) to_date(

yyyymmdd)+

)

where to_char( to_date(yyyymmdd)+rnum D )

not

in ( )

查找间除星期一和七的天数

在前后分别调用DBMS_UTILITYGET_TIME 让后将结果相减(得到的是/ 而不是毫秒)

select months_between(to_date(MMDDYYYY)

to_date(MMDDYYYY)) MONTHS FROM DUAL;

select months_between(to_date(MMDDYYYY)

to_date(MMDDYYYY)) MONTHS FROM DUAL;

Next_day的用法

Next_day(date day)

MondaySunday for format code DAY

MonSun for format code DY

for format code D

select to_char(sysdatehh: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_datehh:mi:ss) from all_objects;

获得小时数

SELECT EXTRACT(HOUR FROM TIMESTAMP ::) from offer

SQL> select sysdate to_char(sysdatehh)from dual;

SYSDATETO_CHAR(SYSDATEHH)

::

SQL> select sysdate to_char(sysdatehh)from dual;

SYSDATETO_CHAR(SYSDATEHH)

::

获取年月日与此类似

年月日的处理

select older_date

newer_date

years

months

abs(

trunc(

newer_date

add_months( older_dateyears*+months )

)

) days

from ( select

trunc(months_between( newer_date older_date )/) YEARS

mod(tr

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