INTERVAL YEAR TO MONTH数据类型

INTERVAL YEAR TO MONTH数据类型

Oracle语法:
INTERVAL 'integer [- integer]' {YEAR | MONTH} [(precision)][TO {YEAR | MONTH}]

该数据类型常用来表示一段时间差, 注意时间差只精确到年和月. precision为年或月的精确域, 有效范围是0到9, 默认值为2.

eg:
INTERVAL '123-2' YEAR(3) TO MONTH    
表示: 123年2个月, "YEAR(3)" 表示年的精度为3, 可见"123"刚好为3为有效数值, 如果该处YEAR(n), n<3就会出错, 注意默认是2.

INTERVAL '123' YEAR(3)
表示: 123年0个月

INTERVAL '300' MONTH(3)
表示: 300个月, 注意该处MONTH的精度是3啊.

INTERVAL '4' YEAR    
表示: 4年, 同 INTERVAL '4-0' YEAR TO MONTH 是一样的

INTERVAL '50' MONTH    
表示: 50个月, 同 INTERVAL '4-2' YEAR TO MONTH 是一样

INTERVAL '123' YEAR    
表示: 该处表示有错误, 123精度是3了, 但系统默认是2, 所以该处应该写成 INTERVAL '123' YEAR(3) 或"3"改成大于3小于等于9的数值都可以的

INTERVAL '5-3' YEAR TO MONTH + INTERVAL '20' MONTH =
INTERVAL '6-11' YEAR TO MONTH
表示: 5年3个月 + 20个月 = 6年11个月

与该类型相关的函数:
NUMTODSINTERVAL(n, 'interval_unit')
将n转换成interval_unit所指定的值, interval_unit可以为: DAY, HOUR, MINUTE, SECOND
注意该函数不可以转换成YEAR和MONTH的.

NUMTOYMINTERVAL(n, 'interval_unit')
interval_unit可以为: YEAR, MONTH

eg: (oracle Version 9204, RedHat Linux 9.0)
SQL> select numtodsinterval(100,'DAY') from dual;

NUMTODSINTERVAL(100,'DAY')                                                     
---------------------------------------------------------------------------    
+000000100 00:00:00.000000000

SQL> c/DAY/SECOND
  1* select numtodsinterval(100,'SECOND') from dual
SQL> /

NUMTODSINTERVAL(100,'SECOND')                                                  
---------------------------------------------------------------------------    
+000000000 00:01:40.000000000

SQL> c/SECOND/MINUTE
  1* select numtodsinterval(100,'MINUTE') from dual
SQL> /

NUMTODSINTERVAL(100,'MINUTE')                                                  
---------------------------------------------------------------------------    
+000000000 01:40:00.000000000

SQL> c/MINUTE/HOUR
  1* select numtodsinterval(100,'HOUR') from dual
SQL> /

NUMTODSINTERVAL(100,'HOUR')                                                    
---------------------------------------------------------------------------    
+000000004 04:00:00.000000000

SQL> c/HOUR/YEAR
  1* select numtodsinterval(100,'YEAR') from dual
SQL> /
select numtodsinterval(100,'YEAR') from dual
                           *
ERROR at line 1:
ORA-01760: illegal argument for function

SQL> select numtoyminterval(100,'year') from dual;

NUMTOYMINTERVAL(100,'YEAR')                                                    
---------------------------------------------------------------------------    
+000000100-00

SQL> c/year/month
  1* select numtoyminterval(100,'month') from dual
SQL> /

NUMTOYMINTERVAL(100,'MONTH')                                                   
---------------------------------------------------------------------------    
+000000008-04

INTERVAL DAY TO SECOND类型存储两个TIMESTAMP之间的时间差异，用日期、小时、分钟、秒钟形式表示。该数据类型的内部代码是183，长度位11字节：

select interval '5' day + interval '10' second from dual

INTERVAL '30.12345' SECOND(2,4)