oracle中extract（）函数----⽤于截取年、⽉、⽇、时、分、秒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 } )
只可以从⼀个date类型中截取年⽉⽇
SQL>select  extract (year from sysdate) year, extract (month from sysdate) month, extract (day from sysdate) day from  dual;
YEAR MONTH DAY
---------- ---------- ----------
201554
只可以从⼀个date类型中截取年⽉⽇
SQL>select extract (year from date '2015-05-04') year, extract (month from date'2015-05-04') month, extract (day from date '2011-05-04') day from dual;
YEAR MONTH DAY
---------- ---------- ----------
201554
从timestamp中获取年⽉⽇时分秒
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
获取两个⽇期之间的具体时间间隔
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
)
oracle四舍五入获取interval类型特定部分
select extract(year from interval '21'year) year from dual
Interval 语法
interval '{ integer | integer time_expr | time_expr }'
{ { day| hour | minute } [ ( leading_precision ) ]
| second [ ( leading_precision [, fractional_seconds_precision ] ) ] }
[ to { day | hour | minute | second [ (fractional_seconds_precision) ] } ]
leading_precision值的范围是0到9, 默认是2. time_expr的格式为:hh[:mi[:ss[.n]]] or mi[:ss[.n]] or ss[.n], n表⽰微秒.
范围值:
hour: 0 to 23
minute: 0 to 59
second: 0 to 59.999999999
eg:
interval '4 5:12:10.222' day to second(3)                表⽰: 4天5⼩时12分10.222秒
interval '4 5:12' day to minute                        表⽰: 4天5⼩时12分
interval '400 5' day(3) to hour                        表⽰: 400天5⼩时, 400为3为精度，所以"day(3)", 注意默认值为2.
interval '400' day(3)                                  表⽰: 400天
interval '11:12:10.2222222' hour to second(7)          表⽰: 11⼩时12分10.2222222秒
interval '11:20' hour to minute                        表⽰: 11⼩时20分
interval '10' hour                                      表⽰: 10⼩时
interval '10:22' minute to second                        表⽰: 10分22秒
interval '10' minute                                    表⽰: 10分
interval '4' day                                        表⽰: 4天
interval '25' hour                                        表⽰: 25⼩时
interval '40' minute                                    表⽰: 40分
interval '120' hour(3)                                    表⽰: 120⼩时
interval '30.12345' second(2,4)                        表⽰: 30.1235秒, 因为该地⽅秒的后⾯精度设置为4, 要进⾏四舍五⼊.
interval '20' day - interval '240' hour = interval '10-0' day to second 表⽰: 20天 - 240⼩时 = 10天0秒

版权声明：本站内容均来自互联网，仅供演示用，请勿用于商业和其他非法用途。如果侵犯了您的权益请与我们联系QQ:729038198，我们将在24小时内删除。