oracle extract截取时间值函数

--用于从date或interval类型中截取特定的值

--语法如下：

EXTRACT ( 
        { YEAR | MONTH | DAY | HOUR | MINUTE | SECOND } 
        | { TIMEZONE_HOUR | TIMEZONE_MINUTE } 
        | { TIMEZONE_REGION | TIMEZONE_ABBR } 
FROM { date_value | interval_value } )

1.date类型日期截取

从一个date类型中截取 year,month,day(date日期的格式为yyyy-mm-dd);

1)截取日期的year

SELECT extract(YEAR FROM date'2012-10-12') YEAR from;

-------2012

SELECT extract(YEAR FROM SYSDATE) YEAR FROM dual;

-------2012

2)截取日期的month

SELECT extract(MONTH FROM date'2012-10-12') YEAR from dual;

-------10

SELECT extract(MONTH FROM SYSDATE) YEAR FROM dual;

------10

3)截取日期的day

SELECT extract(DAY FROM date'2012-10-12') YEAR from dual; 

---------12

SELECT extract(DAY FROM SYSDATE) YEAR FROM dual;

---------12

2.获取两个日期之间的具体时间间隔

select extract(day from dt2-dt1) day 
      ,extract(hour from dt2-dt1) hour 
      ,extract(minute from dt2-dt1) minute 
      ,extract(second from dt2-dt1) second 
from ( 
     select to_timestamp('2012-02-04 15:07:00','yyyy-MM-dd hh24:mi:ss') dt1 
           ,to_timestamp('2012-10-12 17:08:46','yyyy-MM-dd hh24:mi:ss') dt2 
     from dual)

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

day                    hour                      minute               second

251                    2                              1                        46