Oracle中的日期相关函数(部分)

日期和字符转换函数用法

日期转化为字符串

select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') as nowTime from dual;
//获取时间的年
select to_char(sysdate,'yyyy') as nowYear   from dual;
//获取时间的月
select to_char(sysdate,'mm')    as nowMonth from dual;
//获取时间的日
select to_char(sysdate,'dd')    as nowDay    from dual;
//获取时间的时
select to_char(sysdate,'hh24') as nowHour   from dual;
//获取时间的分
select to_char(sysdate,'mi')    as nowMinute from dual;
//获取时间的秒
select to_char(sysdate,'ss')    as nowSecond from dual;

字符串转换成日期

select to_date('2017-05-07 13:23:44','yyyy-mm-dd hh24:mi:ss')    from dual

获取当前日期

select sysdate from dual;

求某天是星期几

select to_char(to_date('2017-06-06','yyyy-mm-dd'),'day') from dual;

select to_char(to_date('2017-06-06','yyyy-mm-dd'),'day','NLS_DATE_LANGUAGE = American') from dual;

求两个日期间的天数

select floor(sysdate - to_date('20070405','yyyymmdd')) from dual;

求两个日期间的月份数

select months_between(to_date('01-31-2018','MM-DD-YYYY'),to_date('12-31-1998','MM-DD-YYYY')) "MONTHS" FROM DUAL;

Next_day（date,char）

select next_day(sysdate,'星期日') from dual;

一年中的第几天

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

两个日期之间的小时数

select (sysdate-to_date('2017-06-06 12:00:00','yyyy-mm-dd hh24:mi:ss'))*24 from dual

舍入到最接近的日期

select sysdate S1,
round(sysdate) S2,
round(sysdate, 'year') YEAR,
round(sysdate, 'month') MONTH,
round(sysdate, 'day') DAY
from dual;

获取月的第一天,最后一天

SELECT
Trunc(SYSDATE, 'MONTH') First_Day_Cur_Month,
LAST_DAY(Trunc(SYSDATE, 'MONTH')) + 1 - 1 / 86400 Last_Day_Cur_Month
FROM dual;

获取最后指定日期所在月份的最后一天

SELECT LAST_DAY(HIREDATE) FROM EMP;

获取某年有多少天

select add_months(trunc(to_date('2004-01-10', 'yyyy-mm-dd'), 'year'), 12) -
trunc(to_date('2004-01-01', 'yyyy-mm-dd'), 'year')
from dual

截取年月日

截取当前时间的年份

SELECT EXTRACT(YEAR FROM SYSDATE) FROM DUAL;

截取月份

SELECT EXTRACT(MONTH FROM SYSDATE) FROM DUAL;

截取日期

SELECT EXTRACT(DAY FROM SYSDATE) FROM DUAL;