获得当前日期、时间函数
获得当前日期时间,now()
select now();
2018-08-08 22:20:46
获得当前时间戳,current_timestamp,current_timestamp()
select current_timestamp, current_timestamp();
2018-08-08 22:28:21
2018-08-08 22:28:21
日期转换函数,时间转换函数
Date/Time to Str(日期/时间转换为字符串)函数:date_format(date,format), time_format(time,format)
select date_format('2018-08-08 22:23:01', '%Y%m%d%H%i%s');
select time_format('2018-08-08 22:23:01', '%Y%m%d%H%i%s');
20180808222301
00000000222301
Str to Date (字符串转换为日期)函数:str_to_date(str, format)
select str_to_date('08/09/2018', '%m/%d/%Y'); -- 2018-08-09
select str_to_date('08/09/08' , '%m/%d/%y'); -- 2018-08-09
select str_to_date('08.09.2018', '%m.%d.%Y'); -- 2018-08-09
select str_to_date('08:09:30', '%h:%i:%s'); -- 08:09:30
select str_to_date('08.09.2018 08:09:30', '%m.%d.%Y %h:%i:%s'); -- 2018-08-09 08:09:30
(日期、天数)转换函数:to_days(date), from_days(days)
select to_days('0000-00-00'); -- 0
select to_days('2018-08-08'); -- 733627
(时间、秒)转换函数:time_to_sec(time), sec_to_time(seconds)
select time_to_sec('01:00:05'); -- 3605
select sec_to_time(3605); -- '01:00:05'
拼凑日期、时间函数:makdedate(year,dayofyear), maketime(hour,minute,second)
select makedate(2018,31); -- '2018-01-31'
select makedate(2018,32); -- '2018-02-01'
select maketime(12,15,30); -- '12:15:30'
(Unix 时间戳、日期)转换函数
unix_timestamp(),
unix_timestamp(date),
from_unixtime(unix_timestamp),
from_unixtime(unix_timestamp,format)
示例:
select unix_timestamp(); -- 1534990179
select unix_timestamp('2018-08-08'); -- 1533657600
select unix_timestamp('2018-08-08 10:11:00'); -- 1533694260
select from_unixtime(1534990179); -- '2018-08-08 10:09:39'
select from_unixtime(1533657600); -- '2018-08-08 00:00:00'
select from_unixtime(1533694260); -- '2018-08-08 10:11:00'
select from_unixtime(1534990179, '%Y %D %M %h:%i:%s %x'); -- '2018 23rd August 10:09:39 2018'
日期时间计算函数
为日期增加一个时间间隔:date_add()
set @dt = now();
select @dt; -- 2018-08-23 10:14:03
select date_add(@dt, interval 1 day); -- 2018-08-24 10:14:26
select date_add(@dt, interval 1 hour); -- add 1 hour
select date_add(@dt, interval 1 minute); -- ...
select date_add(@dt, interval 1 second);
select date_add(@dt, interval 1 microsecond);
select date_add(@dt, interval 1 week);
select date_add(@dt, interval 1 month);
select date_add(@dt, interval 1 quarter);
select date_add(@dt, interval 1 year);
select date_add(@dt, interval -1 day); -- sub 1 day
adddate(), addtime()函数,可以用 date_add() 来替代。下面是 date_add() 实现 addtime() 功能示例:
mysql> set @dt = '2018-08-09 12:12:33';
mysql> select date_add(@dt, interval '01:15:30' hour_second);
2018-08-09 13:28:03
-----------------------------------------------
mysql> select date_add(@dt, interval '1 01:15:30' day_second);
2018-08-10 13:28:03
为日期减去一个时间间隔:date_sub()
和date_add()用法一致
mysql> select date_sub('1998-01-01 00:00:00', interval '1 1:1:1' day_second);
1997-12-30 22:58:59
日期、时间相减函数:datediff(date1,date2), timediff(time1,time2)
-- datediff(date1,date2):两个日期相减 date1 - date2,返回天数。
select datediff('2018-08-08', '2018-08-01'); -- 7
select datediff('2018-08-01', '2018-08-08'); -- -7
-- timediff(time1,time2):两个日期相减 time1 - time2,返回 time 差值。
select timediff('2018-08-08 08:08:08', '2018-08-08 00:00:00'); -- 08:08:08
select timediff('08:08:08', '00:00:00'); -- 08:08:08
注意:timediff(time1,time2) 函数的两个参数类型必须相同。
时间戳(timestamp)转换、增、减函数:
timestamp(date) -- date to timestamp
timestamp(dt,time) -- dt + time
timestampadd(unit,interval,datetime_expr) --
timestampdiff(unit,datetime_expr1,datetime_expr2) --
示例:
select timestamp('2018-08-08'); -- 2018-08-08 00:00:00
select timestamp('2018-08-08 08:00:00', '01:01:01'); -- 2018-08-08 09:01:01
select timestamp('2018-08-08 08:00:00', '10 01:01:01'); -- 2018-08-18 09:01:01
select timestampadd(day, 1, '2018-08-08 08:00:00'); -- 2018-08-09 08:00:00
select date_add('2018-08-08 08:00:00', interval 1 day); -- 2018-08-09 08:00:00
-- timestampadd() 函数类似于 date_add()。
select timestampdiff(year,'2018-05-01','2017-01-01'); -- -1
select timestampdiff(day ,'2018-05-01','2017-01-01'); -- -485
select timestampdiff(hour,'2018-08-08 12:00:00','2018-08-08 00:00:00'); -- -12
select datediff('2018-08-08 12:00:00', '2018-08-01 00:00:00'); -- 7
timestampdiff() 函数就比 datediff() 功能强多了,datediff() 只能计算两个日期(date)之间相差的天数。
时区(timezone)转换函数
convert_tz(dt,from_tz,to_tz)
select convert_tz('2018-08-08 12:00:00', '+08:00', '+00:00'); -- 2018-08-08 04:00:00
时区转换也可以通过 date_add, date_sub, timestampadd 来实现。
select date_add('2018-08-08 12:00:00', interval -8 hour); -- 2018-08-08 04:00:00
select date_sub('2018-08-08 12:00:00', interval 8 hour); -- 2018-08-08 04:00:00
select timestampadd(hour, -8, '2018-08-08 12:00:00'); -- 2018-08-08 04:00:00