MySql operation on time

Acquires the current time:

select NOW()

Results: 2020-03-05 23:11:17

Acquisition time before a certain time interval n hours:

select "2020-03-28 23:10:06"+INTERVAL n HOUR

Results: 2020-03-29 01:10:06

Get in a certain time, month, day, hour, minute, second

select upd_time FROM student WHERE id=32;
select year(upd_time) FROM student WHERE id=32;
select MONTH(upd_time) FROM student WHERE id=32;
select DAY(upd_time) FROM student WHERE id=32;
select HOUR(upd_time) FROM student WHERE id=32;
select MINUTE(upd_time) FROM student WHERE id=32;
select SECOND(upd_time) FROM student WHERE id=32;

datediff function returns the number of days between two dates: the first parameter minus the second parameter, in days

SELECT DATEDIFF('2018-07-01','2018-07-04');

The results: -3

TIMESTAMPDIFF calculated time difference between two units can be specified: a first parameter specifies the time difference between the two units, the smaller units, the higher the accuracy, the time difference is subtracted behind the front time

FRAC_SECOND。表示间隔是毫秒
SECOND。秒
MINUTE。分钟
HOUR。小时
DAY。天
WEEK。星期
MONTH。月
QUARTER。季度
YEAR。年
SELECT TIMESTAMPDIFF(MINUTE,'2020-03-28 23:10:06','2020-03-28 20:11:06');

Timestamp is scheduled to be converted to the format:

select FROM_UNIXTIME(1344954515,'%Y-%m-%d %H:%i:%S');

Results: 2012-08-14 22:28:35

A time to a timestamp

select UNIX_TIMESTAMP('2012-08-14 22:28:35'); 

The result is: 1344954515

date_format fixed format is converted to a time period of

select date_format('2020-02-27 14:27:09','%Y-%m-%d')

common format date format is as follows:

%M 月名字(January……December) 
%W 星期名字(Sunday……Saturday) 
%D 有英语前缀的月份的日期(1st, 2nd, 3rd, 等等。） 
%Y 年, 数字, 4 位 
%y 年, 数字, 2 位 
%a 缩写的星期名字(Sun……Sat) 
%d 月份中的天数, 数字(00……31) 
%e 月份中的天数, 数字(0……31) 
%m 月, 数字(01……12) 
%c 月, 数字(1……12) 
%b 缩写的月份名字(Jan……Dec) 
%j 一年中的天数(001……366) 
%H 小时(00……23) 
%k 小时(0……23) 
%h 小时(01……12) 
%I 小时(01……12) 
%i 分钟, 数字(00……59) 
%r 时间,12 小时(hh:mm:ss [AP]M) 
%T 时间,24 小时(hh:mm:ss) 
%S 秒(00……59) 
%s 秒(00……59) 
%p AM或PM 
%w 一个星期中的天数(0=Sunday ……6=Saturday ） 
%U 星期(0……52), 这里星期天是星期的第一天 
%u 星期(0……52), 这里星期一是星期的第一天