本節介紹了基本算術操作符（+，-）的功能和可以用於處理日期/時間類型值的函數。
在表 1中說明了基本算術操作符（+，-）的功能。表 2顯示了所有可以用於處理日期/時間類型值的函數，關於這些函數的更詳細資料將在後面的部分中出現。對于格式化類型的函數，請參見格式化函數（數字、字元、日期類型）。在進行本節的內容學習前，應該從章節日期/時間類型中熟悉日期/時間類型的背景資訊。
表 1. Date/Time Operators
Operator | Example | Result |
+ | DATE '2001-09-28' + 7 | 05-OCT-01 00:00:00 |
+ | TIMESTAMP '2001-09-28 13:30:00' + 3 | 01-OCT-01 13:30:00 |
- | DATE '2001-10-01' - 7 | 24-SEP-01 00:00:00 |
- | TIMESTAMP '2001-09-28 13:30:00' - 3 | 25-SEP-01 13:30:00 |
- | TIMESTAMP '2001-09-29 03:00:00' - TIMESTAMP '2001-09-27 12:00:00' | @ 1 day 15 hours |
在表 2中顯示的日期/時間函數中，DATE和TIMESTAMP資料類型可以互換使用。
表 2. Date/Time Functions
Function | Return Type | Description | Example | Result |
ADD MONTHS(DATE, NUMBER) | DATE | Add months to a date. | ADD MONTHS('28-FEB-97', 3.8) | 31-MAY-97 00:00:00 |
CURRENT DATE | DATE | Current date. | CURRENT DATE | 04-JUL-07 |
CURRENT TIMESTAMP | TIMESTAMP | Returns the current date and time. | CURRENT TIMESTAMP | 04-JUL-07 15:33:23.484 |
EXTRACT(field FROM TIMESTAMP) | DOUBLE PRECISION | Get subfield. | EXTRACT(hour FROM TIMESTAMP '2001-02-16 20:38:40') | 20 |
LAST DAY(DATE) | DATE | Returns the last day of the month represented by the given date. If the given date contains a time portion, it is carried forward to the result unchanged. | LAST DAY('14-APR-98') | 30-APR-98 00:00:00 |
LOCALTIMESTAMP [ (precision) ] | TIMESTAMP | Current date and time (start of current transaction). | LOCALTIMESTAMP | 04-JUL-07 15:33:23.484 |
MONTHS BETWEEN(DATE, DATE) | NUMBER | Number of months between two dates. | MONTHS BETWEEN('28-FEB- 07', '30-N0V-06') | 3 |
NEXT DAY(DATE, dayofweek) | DATE | Date falling on dayofweek following specified date. | NEXT DAY('16-APR- 07','FRI') | 2 0-APR-07 00:00:00 |
NEW TIME(DATE, VARCHAR, VARCHAR) | DATE | Converts a date and time to an alternate time zone | NEW TIME(T0 DATE '2005/05/29 01:45', 'AST', 'PST') | 2005/05/29 21:45:00 |
ROUND(DATE [, format ]) | DATE | Date rounded according to format. | R0UND(T0 DATE('29-MAY- 05'),'M0N') | 01-JUN-05 00:00:00 |
SYS EXTRACT UTC(TIME STAMP WITH TIME ZONE) | TIMESTAMP | TIMESTAMP | SYS EXTRACT UTC(CAST('24 -MAR-11 12:30:00PM - 04:00' AS TIMESTAMP WITH TIME ZONE)) | 2 4-MAR-11 16:30:00 |
SYSDATE | DATE | Returns current date and time | SYSDATE | 01-AUG-12 11:12:34 |
SYSTIMESTAMP() | TIMESTAMP | Returns current date and time | SYSTIMESTAMP | 01-AUG-12 11:11:23.665 229 -07:00 |
TRUNC(DATE [format ]) | DATE | Truncate according to format. | TRUNC(T0 DATE('2 9-MAY- 05'), 'MON') | 01-MAY-05 00:00:00 |