Table of contents
1.MySQL get the current date and time function
1.1 Get the current date (date) function: curdate()
1.2 Get the current time (time) function: curtime()
1.3 Get the current date + time (date + time) function: now()
1.4 Get the current date + time (date + time) function: sysdate()
1.5 Get the current timestamp function: current_timestamp, current_timestamp()
2.MySQL date/time conversion function
2.1 Date/time conversion to string functions: date_format(date,format), time_format(time,format)
2.2 Convert string to date function: str_to_date(str, format)
2.3 Date/day conversion function: to_days(date), from_days(days)
2.4 Time/second conversion function: time_to_sec(time), sec_to_time(seconds)
2.5 Make up date/time functions: makdedate(year,dayofyear), maketime(hour,minute,second)
2.6 Unix timestamp/date conversion functions
3. MySQL date and time calculation function
3.1 Add a time interval to the date: date_add()
3.2 Subtract a time interval from a date: date_sub()
3.3 Date and time subtraction function: datediff(date1,date2), timediff(time1,time2)
3.4 Timestamp (timestamp) conversion, increase and decrease functions:
4.MySQL time zone (timezone) conversion function: convert_tz(dt,from_tz,to_tz)
1.MySQL get the current date and time function
1.1 Get the current date (date) function: curdate()
1.2 Get the current time (time) function: curtime()
1.3 Get the current date + time (date + time) function: now()
1.4 Get the current date + time (date + time) function: sysdate()
sysdate() is similar to now(), the difference is: now() gets the value at the beginning of execution, and sysdate() gets the value dynamically when the function is executed.
See the following example to understand:
1.5 Get the current timestamp function: current_timestamp, current_timestamp()
2.MySQL date/time conversion function
2.1 Date/time conversion to string functions: date_format(date,format), time_format(time,format)
MySQL date and time conversion functions: date_format(date,format), time_format(time,format) can convert a date/time into various string formats.
It is an inverse conversion of the str_to_date(str,format) function.
2.2 Convert string to date function: str_to_date(str, format)
str_to_date(str,format) conversion function, which can convert some messy strings into date format.
Alternatively, it can be converted to time as well. "format" can refer to the MySQL manual.
select str_to_date('05/08/2023', '%m/%d/%Y'); -- 2023-05-08
select str_to_date('05/08/2023' , '%m/%d/%y'); -- 2023-05-08
select str_to_date('05.08.2023', '%m.%d.%Y'); -- 2023-05-08
select str_to_date('12:32:24', '%h:%i:%s'); -- 00:32:24
select str_to_date('05.08.2023 12:32:24', '%m.%d.%Y %h:%i:%s'); -- 2023-05-08 12:32:24
2.3 Date/day conversion function: to_days(date), from_days(days)
select to_days('0000-01-01'); -- 1(日期转换为天数)
select to_days(curdate()); -- 739013(日期转换为天数)
select from_days(0); -- 0000-00-00(天数转换为日期)
select from_days(739013); -- 2023-05-08(天数转换为日期)
2.4 Time/second conversion function: time_to_sec(time), sec_to_time(seconds)
select time_to_sec('01:00:05'); -- 3605(时间转换为秒数)
select sec_to_time(3605); -- 01:00:05(秒数转换为时间)
2.5 Make up date/time functions: makdedate(year,dayofyear), maketime(hour,minute,second)
select makedate(2020,31); -- 2020-01-3(拼凑日期)
select makedate(2020,32); -- 2020-02-01(拼凑日期)
select maketime(12,15,30); -- 12:15:30(拼凑时间)
2.6 Unix timestamp/date conversion functions
unix_timestamp(),
unix_timestamp(date),
from_unixtime(unix_timestamp),
from_unixtime(unix_timestamp,format)
select unix_timestamp(); -- 1683544672
select from_unixtime(1683544672); -- 2023-05-08 19:17:52
select unix_timestamp(curdate()); -- 1683475200
select from_unixtime(1683475200); -- 2023-05-08 00:00:00
select unix_timestamp(current_timestamp()); -- 1683544792
select from_unixtime(1683544792); -- 2023-05-08 19:19:52
select from_unixtime(1683544672, '%Y %D %M %h:%i:%s %x'); -- 2023 8th May 07:17:52 20233. MySQL date and time calculation function
3.1 Add a time interval to the date: date_add()
set @dt = now();
select @dt;
select date_add(@dt, interval 1 day); -- add 1 day
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
MySQL adddate(), addtime() functions can be replaced by date_add().
The following is an example of date_add() implementing the addtime() function:
mysql> set @dt = now();
mysql> select date_add(@dt, interval '01:15:30' hour_second);
+------------------------------------------------+
| date_add(@dt, interval '01:15:30' hour_second) |
+------------------------------------------------+
| 2023-05-08 20:47:09 |
+------------------------------------------------+
mysql> select date_add(@dt, interval '1 01:15:30' day_second);
+-------------------------------------------------+
| date_add(@dt, interval '1 01:15:30' day_second) |
+-------------------------------------------------+
| 2023-05-09 20:47:09 |
+-------------------------------------------------+
3.2 Subtract a time interval from a date: date_sub()
The MySQL date_sub() datetime function is used in the same way as date_add().
mysql> set @dt = now();
mysql> select date_sub(@dt, interval '1 1:1:1' day_second);
+----------------------------------------------------------------+
| date_sub('2020-07-24 12:02:05', interval '1 1:1:1' day_second) |
+----------------------------------------------------------------+
| 2023-05-07 18:32:28 |
+----------------------------------------------------------------+
3.3 Date and time subtraction function: datediff(date1,date2), timediff(time1,time2)
MySQL datediff(date1, date2): subtract date1 - date2 from two dates, and return the number of days.
mysql> select datediff(curdate(), '2023-05-01'); -- 7
mysql> select datediff('2023-05-01', '2023-05-08'); -- -7
MySQL timediff(time1,time2): subtract time1 - time2 from two dates, and return the time difference.
mysql> select timediff(current_timestamp(), '2023-05-08 00:00:00'); -- 19:39:20
mysql> select timediff('19:39:20', '00:00:00'); -- 19:39:20
Note: The two parameters of the timediff(time1,time2) function must be of the same type.
3.4 Timestamp (timestamp) conversion, increase and decrease functions:
timestamp(date) – date to timestamp
timestamp(dt,time) – dt + time
timestampadd(unit,interval,datetime_expr)
timestampdiff(unit,datetime_expr1,datetime_expr2)
-- 转换
select timestamp('2023-05-08'); -- 2023-05-08 00:00:00
select timestamp('2023-05-08 19:52:51', '01:01:01'); -- 2023-05-08 20:53:52
select timestamp(current_timestamp(), '10 01:01:01'); -- 2023-05-18 20:54:46
-- 增
select timestampadd(day, 1, current_timestamp()); -- 2023-05-09 19:54:26
select date_add(current_timestamp(), interval 1 day); -- 2023-05-09 19:55:06
-- 减
select timestampdiff(year,current_timestamp(),'2018-01-01'); -- -5
select timestampdiff(day ,'2023-05-08','2018-01-01'); -- -1953
select timestampdiff(hour,'2023-05-08 12:00:00','2023-05-08 00:00:00'); -- -12
select datediff('2023-05-08 12:00:00', '2023-05-01 00:00:00'); -- 7
# MySQL 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。
4.MySQL time zone (timezone) conversion function: convert_tz(dt,from_tz,to_tz)
select convert_tz('2023-05-08 12:00:00', '+08:00', '+00:00'); -- 2023-05-08 04:00:00
# 时区转换也可以通过 date_add, date_sub, timestampadd 来实现。
select date_add('2023-05-08 12:00:00', interval -8 hour); -- 2023-05-08 04:00:00
select date_sub('2023-05-08 12:00:00', interval 8 hour); -- 2023-05-08 04:00:00
select timestampadd(hour, -8, '2023-05-08 12:00:00'); -- 2023-05-08 04:00:00