oracle extract()截取时间值函数

//oracle中extract()函数从oracle 9i中引入,用于从一个date或者interval类型中截取到特定的部分//语法如下：EXTRACT ( { YEAR | MONTH | DAY | HOUR | MINUTE | SECOND } | { TIMEZONE_HOUR | TIMEZONE_MINUTE } | { TIMEZONE_REGION | TIMEZONE_ABBR }FROM { date_value | interval_value } )//我们只可以从一个date类型中截取 year,month,day(date日期的格式为yyyy-mm-dd);//我们只可以从一个 timestamp with time zone 的数据类型中截取TIMEZONE_HOUR和TIMEZONE_MINUTE;select extract(year from date'2011-05-17') year from dual; YEAR---------- 2011select extract(month from date'2011-05-17') month from dual; MONTH---------- 5select extract(day from date'2011-05-17') day from dual; DAY---------- 17//获取两个日期之间的具体时间间隔，extract函数是最好的选择select extract(day from dt2-dt1) day ,extract(hour from dt2-dt1) hour ,extract(minute from dt2-dt1) minute ,extract(second from dt2-dt1) secondfrom ( select to_timestamp('2011-02-04 15:07:00','yyyy-mm-dd hh24:mi:ss') dt1 ,to_timestamp('2011-05-17 19:08:46','yyyy-mm-dd hh24:mi:ss') dt2 from dual)/ DAY HOUR MINUTE SECOND---------- ---------- ---------- ---------- 102 4 1 46--select extract(year from systimestamp) year ,extract(month from systimestamp) month ,extract(day from systimestamp) day ,extract(minute from systimestamp) minute ,extract(second from systimestamp) second ,extract(timezone_hour from systimestamp) th ,extract(timezone_minute from systimestamp) tm ,extract(timezone_region from systimestamp) tr ,extract(timezone_abbr from systimestamp) tafrom dual/ YEAR MONTH DAY MINUTE SECOND TH TM TR TA---------- ---------- ---------- ---------- ---------- ---------- ---------- --------- ---------- 2011 5 17 7 14.843 8 0 UNKNOWN UNK// 

参考 Extract Function：

http://www.techonthenet.com/oracle/functions/extract.php