2014-12-08 Created By BaoXinjian
INTERVAL数据类型用来存储两个时间戳之间的时间间隔。
可以指定years and months，或者days，hours，minuts，seconds之间的间隔。
ORACLE支持两种INTEVAL类型，它们分别是YEAR TO MONTH和DAY TO SECOND。
每个类型都包含leading field和trailing field。主参数定义要被计算的date或者time，副参数定义最小增长量
1. Oracle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) ] } ]
(1). 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.
(2). 该类型与INTERVAL YEAR TO MONTH有很多相似的地方,建议先看INTERVAL YEAR TO MONTH再看该文.
2. 范围值:
HOUR: 0 to 23
MINUTE: 0 to 59
SECOND: 0 to 59.999999999
1. 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
2. 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
3. 其他
select date '2010-01-01' + interval '21' year from dual
select date '2010-01-01' + interval '123-2' year(4) to month from dual
select date '2010-01-01' + interval '100' month from dual
select date '2010-01-01' + interval '100' day(2) from dual
select date '2010-01-01' + interval '1 2' day to hour from dual
select date '2010-01-01' + interval '1 2:3' day to minute from dual
select date '2010-01-01' + interval '1 2:3:4' day to second from dual
select date '2010-01-01' + interval '1' hour from dual
select date '2010-01-01' + interval '1:2' hour to minute from dual
select date '2010-01-01' + interval '1:2:3' hour to second from dual
select date '2010-01-01' + interval '1:2' minute to second from dual
Thanks and Regards
