- //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
- ----------
- 2011
- select extract(month from date'2011-05-17') month from dual;
- MONTH
- ----------
- 5
- select 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) second
- from (
- 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) ta
- from dual
- /
- YEAR MONTH DAY MINUTE SECOND TH TM TR TA
- ---------- ---------- ---------- ---------- ---------- ---------- ---------- --------- ----------
- 2011 5 17 7 14.843 8 0 UNKNOWN UNK