spark日期处理

详情查看：https://www.cnblogs.com/feiyumo/p/8760846.html

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一、获取当前时间
1.current_date获取当前日期

2018-04-09
2.current_timestamp/now()获取当前时间

2018-04-09 15:20:49.247
二、从日期时间中提取字段
1.year,month,day/dayofmonth,hour,minute,second

Examples:> SELECT day(‘2009-07-30’); 30
2.dayofweek (1 = Sunday, 2 = Monday, …, 7 = Saturday),dayofyear

Examples:> SELECT dayofweek(‘2009-07-30’);　　 5

Since: 2.3.0
3.weekofyear

weekofyear(date) - Returns the week of the year of the given date. A week is considered to start on a Monday and week 1 is the first week with >3 days.

Examples:> SELECT weekofyear(‘2008-02-20’);　　 8
6.date_format将时间转化为某种格式的字符串

Examples:> SELECT date_format(‘2016-04-08’, ‘y’);　　　　2016
三、日期时间转换
1.unix_timestamp返回当前时间的unix时间戳

Examples:

> SELECT unix_timestamp();　　1476884637
> SELECT unix_timestamp('2016-04-08', 'yyyy-MM-dd');　　 1460041200

2.from_unixtime将时间戳换算成当前时间，to_unix_timestamp将时间转化为时间戳

Examples:

> SELECT from_unixtime(0, 'yyyy-MM-dd HH:mm:ss');　　1970-01-01 00:00:00
>SELECT to_unix_timestamp('2016-04-08', 'yyyy-MM-dd');　　
1460041200

3.to_date/date将字符串转化为日期格式，to_timestamp（Since: 2.2.0）

> SELECT to_date('2009-07-30 04:17:52');　　2009-07-30
> SELECT to_date('2016-12-31', 'yyyy-MM-dd');　　 2016-12-31

SELECT to_timestamp(‘2016-12-31 00:12:00’);　　 2016-12-31 00:12:00

4.quarter 将1年4等分(range 1 to 4)

Examples:> SELECT quarter(‘2016-08-31’); 3
四、日期、时间计算
1.months_between两个日期之间的月数

months_between(timestamp1, timestamp2) - Returns number of months between timestamp1 and timestamp2.

Examples:> SELECT months_between(‘1997-02-28 10:30:00’, ‘1996-10-30’);　　3.94959677
2. add_months返回日期后n个月后的日期

Examples:> SELECT add_months(‘2016-08-31’, 1);　　2016-09-30
3.last_day(date),next_day(start_date, day_of_week)

Examples:

SELECT last_day(‘2009-01-12’);　　2009-01-31

SELECT next_day(‘2015-01-14’, ‘TU’);　　2015-01-20

4.date_add,date_sub(减)

date_add(start_date, num_days) - Returns the date that is num_days after start_date.

Examples:

SELECT date_add(‘2016-07-30’, 1);　　2016-07-31

5.datediff（两个日期间的天数）

datediff(endDate, startDate) - Returns the number of days from startDate to endDate.

Examples:> SELECT datediff(‘2009-07-31’, ‘2009-07-30’); 1