PL / SQL-日期和时间

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📜 PL / SQL-日期和时间

📅 最后修改于: 2020-11-26 06:03:33 🧑 作者: Mango

在本章中，我们将讨论PL / SQL中的日期和时间。 PL / SQL中有两类与日期和时间相关的数据类型-

日期时间数据类型是-

间隔数据类型为-

日期时间和间隔数据类型的字段值

datetime和interval数据类型都由字段组成。这些字段的值确定数据类型的值。下表列出了日期时间和间隔的字段及其可能的值。

Field Name	Valid Datetime Values	Valid Interval Values
YEAR	-4712 to 9999 (excluding year 0)	Any nonzero integer
MONTH	01 to 12	0 to 11
DAY	01 to 31 (limited by the values of MONTH and YEAR, according to the rules of the calendar for the locale)	Any nonzero integer
HOUR	00 to 23	0 to 23
MINUTE	00 to 59	0 to 59
SECOND	00 to 59.9(n), where 9(n) is the precision of time fractional seconds The 9(n) portion is not applicable for DATE.	0 to 59.9(n), where 9(n) is the precision of interval fractional seconds
TIMEZONE_HOUR	-12 to 14 (range accommodates daylight savings time changes) Not applicable for DATE or TIMESTAMP.	Not applicable
TIMEZONE_MINUTE	00 to 59 Not applicable for DATE or TIMESTAMP.	Not applicable
TIMEZONE_REGION	Not applicable for DATE or TIMESTAMP.	Not applicable
TIMEZONE_ABBR	Not applicable for DATE or TIMESTAMP.	Not applicable

以下是Datetime数据类型-

它以字符和数字数据类型存储日期和时间信息。它由世纪，年，月，日，时，分和秒的信息组成。它指定为-

它是DATE数据类型的扩展。它存储DATE数据类型的年，月和日，以及时，分和秒值。这对于存储精确的时间值很有用。

它是TIMESTAMP的一种变体，在其值中包含时区区域名称或时区偏移。时区偏移量是当地时间与UTC之间的时差(以小时和分钟为单位)。此数据类型对于跨地理区域收集和评估日期信息很有用。

它是TIMESTAMP的另一个变体，其值包含时区偏移。

下表提供了Datetime函数(其中，x具有datetime值)-

S.No	Function Name & Description
1	ADD_MONTHS(x, y); Adds y months to x.
2	LAST_DAY(x); Returns the last day of the month.
3	MONTHS_BETWEEN(x, y); Returns the number of months between x and y.
4	NEXT_DAY(x, day); Returns the datetime of the next day after x.
5	NEW_TIME; Returns the time/day value from a time zone specified by the user.
6	ROUND(x [, unit]); Rounds x.
7	SYSDATE(); Returns the current datetime.
8	TRUNC(x [, unit]); Truncates x.

时间戳函数(其中，x具有时间戳值)-

S.No	Function Name & Description
1	CURRENT_TIMESTAMP(); Returns a TIMESTAMP WITH TIME ZONE containing the current session time along with the session time zone.
2	EXTRACT({ YEAR \| MONTH \| DAY \| HOUR \| MINUTE \| SECOND } \| { TIMEZONE_HOUR \| TIMEZONE_MINUTE } \| { TIMEZONE_REGION \| } TIMEZONE_ABBR ) FROM x) Extracts and returns a year, month, day, hour, minute, second, or time zone from x.
3	FROM_TZ(x, time_zone); Converts the TIMESTAMP x and the time zone specified by time_zone to a TIMESTAMP WITH TIMEZONE.
4	LOCALTIMESTAMP(); Returns a TIMESTAMP containing the local time in the session time zone.
5	SYSTIMESTAMP(); Returns a TIMESTAMP WITH TIME ZONE containing the current database time along with the database time zone.
6	SYS_EXTRACT_UTC(x); Converts the TIMESTAMP WITH TIMEZONE x to a TIMESTAMP containing the date and time in UTC.
7	TO_TIMESTAMP(x, [format]); Converts the string x to a TIMESTAMP.
8	TO_TIMESTAMP_TZ(x, [format]); Converts the string x to a TIMESTAMP WITH TIMEZONE.

以下代码段说明了上述功能的用法-

例子1

SELECT SYSDATE FROM DUAL;

输出–

08/31/2012 5:25:34 PM

例子2

SELECT TO_CHAR(CURRENT_DATE, 'DD-MM-YYYY HH:MI:SS') FROM DUAL;

输出–

31-08-2012 05:26:14

例子3

SELECT ADD_MONTHS(SYSDATE, 5) FROM DUAL;

输出–

01/31/2013 5:26:31 PM

例子4

SELECT LOCALTIMESTAMP FROM DUAL;

输出–

8/31/2012 5:26:55.347000 PM

以下是间隔数据类型-

S.No	Function Name & Description
1	NUMTODSINTERVAL(x, interval_unit); Converts the number x to an INTERVAL DAY TO SECOND.
2	NUMTOYMINTERVAL(x, interval_unit); Converts the number x to an INTERVAL YEAR TO MONTH.
3	TO_DSINTERVAL(x); Converts the string x to an INTERVAL DAY TO SECOND.
4	TO_YMINTERVAL(x); Converts the string x to an INTERVAL YEAR TO MONTH.