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日期时间运算符

运算符	示例	结果
+	date ‘2012-08-08’ + interval ‘2’ day )	2012-08-10
+	time ‘01:00’ + interval ‘3’ hour	04:00:00.000
+	timestamp ‘2012-08-08 01:00’ + interval ‘29’ hour	2012-08-09 06:00:00.000
+	timestamp ‘2012-10-31 01:00’ + interval ‘1’ month	2012-11-30 01:00:00.000
+	interval ‘2’ day + interval ‘3’ hour	2 03:00:00.000
+	interval ‘3’ year + interval ‘5’ month	3-5
-	date ‘2012-08-08’ - interval ‘2’ day	2012-08-06
-	time ‘01:00’ - interval ‘3’ hour	22:00:00.000
-	dtimestamp ‘2012-08-08 01:00’ - interval ‘29’ hour	2012-08-06 20:00:00.000
-	timestamp ‘2012-10-31 01:00’ - interval ‘1’ month	2012-09-30 01:00:00.000
-	interval ‘2’ day - interval ‘3’ hour	1 21:00:00.000
-	interval ‘3’ year - interval ‘5’ month	2-7

时区转换
运算符：AT TIME ZONE，用于设置一个时间戳的时区:

select timestamp '2022-03-17 01:00 UTC';
2022-03-17 09:00:00

select timestamp '2022-03-17 01:00 UTC' AT TIME ZONE 'America/Los_Angeles';
2022-03-17 09:00:00

获取当前日期：current_date()

select current_date();
-- 2022-03-17

获取当前时间：current_time()

select current_time();
-- 17:07:16

获取当前日期和时间：current_timestamp()

select current_timestamp();
-- 2022-03-17 21:17:49.035

获取当前日期和时间：now()

select now();
-- 2022-03-17 21:27:03.604

获取当前时区：current_timezone()

select current_timezone(); 
-- Asia/Shanghai

字符串转时间戳：cast(string, timestamp)

select cast('2022-03-17' as timestamp);
-- 2022-03-17 00:00:00.0
select cast('2022-03-17 00:00:00' as timestamp);
-- 2022-03-17 00:00:00.0

字符串转时间戳：date_parse(string, fromat)

select date_parse('2022-03-17', '%Y-%m-%d');
-- 2022-03-17 00:00:00.0
select date_parse('2022-03-17 00:00:00', '%Y-%m-%d %H:%i:%S');
-- 2022-03-17 00:00:00.0

注意： 字符串格式和format格式需保持一致。
以下为错误示例：

select date_parse('2022-03-17', '%Y-%m-%d %H:%i:%S');
-- Invalid format: "2022-03-17" is too short

bigint转时间戳

select from_unixtime(1647500800);
-- 2022-03-17 15:06:40.0

时间戳转biging

select to_unixtime(current_date);
-- 1647446400

时间戳格式化： format_datetime(timestamp,format)

select format_datetime(cast('2022-03-17' as timestamp),'yyyy-MM-dd HH:mm:ss');
-- 2022-03-17 00:00:00
select format_datetime(cast('2022-03-17' as timestamp),'yyyy-MM-dd HH');
-- 2022-03-17 00
select date_trunc('second', current_timestamp());
-- 2022-05-03 13:37:12.0
select date_trunc('minute', current_timestamp());
-- 

时间戳取年月日

select date_format(current_date,'%Y-%m-%d');
select date(current_date);
select cast(current_date as date);
-- 2022-03-17

字符串转年月日

select date(cast('2021-03-17 10:28:00' as TIMESTAMP));
select date('2021-03-17');
select date_format(cast('2021-03-17 10:28:00' as TIMESTAMP),'%Y-%m-%d');
select to_date('2021-03-17','yyyy-mm-dd');
 -- 2021-03-17

注意： 格式不同时date、to_date无法使用

select date('2021-03-17 10:28:00');
-- Value cannot be cast to date: 2021-03-17 10:28:00
select to_date('2021-03-17 10:28:00','yyyy-mm-dd');
-- Invalid format: "2021-03-17 10:28:00" is malformed at " 10:28:00"

bigint转年月日

select date(from_unixtime(1647500800));
-- 2022-03-17
select date_format(from_unixtime(1647500800),'%Y-%m-%d');
-- 2022-03-17

时间间隔：date_diff(unit, timestamp1, timestamp2)

函数支持如下所列的间隔单位：

Unit	Description
second	Seconds
minute	Minutes
hour	Hours
day	Days
week	Weeks
month	Months
quarter	Quarters of a year
year	Years

select date_diff('day',cast('2022-03-17' as TIMESTAMP),cast('2022-03-26' as TIMESTAMP));
-- 9
select date_diff('month',cast('2022-02-17' as TIMESTAMP),cast('2022-03-26' as TIMESTAMP));
-- 1
select date_diff('year',cast('2021-02-17' as TIMESTAMP),cast('2022-03-26' as TIMESTAMP));
-- 1

注意： 与hive差异！！！

presto中 date_diff('day',date1,date2)【后-前】
hive,mysql中 datediff(date1,date2) 【前-后】

几天前后几天后：interval、date_add

select current_date, (current_date - interval '7' month), date_add('day', -7, current_date);
-- 2022-03-17 | 2021-08-17 | 2022-03-10
select current_date, (current_date + interval '7' month), date_add('day', 7, current_date);
-- 2022-03-17 | 2022-10-17 | 2022-03-24

月初、年初、周一和季度第一天：date_trunc(unit, timestamp)

函数 date_trunc支持如下单位：

单位	Example Truncated Value
second	2001-08-22 03:04:05.000
minute	2001-08-22 03:04:00.000
hour	2001-08-22 03:00:00.000
day	2001-08-22 00:00:00.000
week	2001-08-20 00:00:00.000
month	2001-08-01 00:00:00.000
quarter	2001-07-01 00:00:00.000
year	2001-01-01 00:00:00.000

上面的例子使用时间戳： 2001-08-22 03:04:05.321 作为输入。

select date_trunc('second', current_timestamp());
-- 2022-05-03 13:39:38.0
select date_trunc('minute', current_timestamp());
-- 2022-05-03 13:40:00.0
select date_trunc('hour', current_timestamp());
-- 2022-05-03 13:00:00.0
select date_trunc('day', current_timestamp());
-- 2022-05-03 00:00:00.0
select date_trunc('week', cast('2022-03-17' as date));
-- 2022-03-14
select date_trunc('month', cast('2022-03-17' as date));
-- 2022-03-01
select date_trunc('quarter', cast('2022-03-17' as date));
-- 2022-01-01
select date_trunc('year', cast('2022-03-17' as date));
-- 2022-01-01

时间提取函数 extract、year、month、day

select 
	extract(year from current_date),
	year(current_date),
	extract(month from current_date),
	month(current_date),
	extract(day from current_date),
	day(current_date);
-- 2022 | 2022 | 3 | 3 | 17 | 17

日期是周几：day_of_week()

select day_of_week(current_date)
-- 4