Date time type and format in MySQL

Catalog

【1】MySQL Date time type in

① Explain in detail

② SQL Statement instance

③ timestamp Field

④ Test case

【2】 Format date time type ① DATE_FORMAT( ) function

② date_format( ) Transformation format

③ str_to_date() function

【1】MySQL Date time type in

MySQL There are several time types commonly used in ：date、datetime、time、year、timestamp

The data type occupies the minimum value and the maximum value of bytes. The zero value indicates

date	4	1000-01-01	9999-12-31	0000-00-00
datetime	8	1000-01-01 00:00:00	9999-12-31 23:59:59	0000-00-00 00:00: 00
timestamp	4	19700101080001	2038 Some time in the year	0000000000000000
time	3	-838:59:59	838:59:59	00:00:00
year	1	1901	2155	0000

① Explain in detail

datetime : Time date type , The format is YYYY-mm-dd HH:ii:ss, The range of representation is from 1000 To 9999. But it has zero value ,0000-00-00 00:00:00;

date： date , Namely datetime Medium date part ;

time： Time ( paragraph ), Between a specified interval , from - Time out + Time ( Negative time indicates );

timestamp： Time stamp , It's not a regular timestamp ( Such as ：14253685), The scope is ’1970-01-01 00:00:00’ To 2037 year . The format is YYYY-mm-dd HH:ii:ss, Format and datetime Exactly the same ;

year：yy and yyyy,yyyy The range is 1901-2155,yy The range is 1970-2069.

Two of you year(00-69 Express 2000-2069,70-99 Express 1970~1999). When the application only needs to record the year ,year Than date More save a space

② SQL Statement instance create table my_date(d1 datetime,d2 date,d3 time,d4 timestamp,d5 year)charset utf8;desc my_date

As shown in the figure below ：year The default is 4 position , namely YYYY; timestamp Can't be empty , Have default values , Refresh this data column when creating new records and modifying existing records .

Insert several pieces of data as follows and correct time Do difference analysis ：

insert into my_date VALUES('2015-09-28 11:50:36','2015-09-28','11:50:54','2015-09-28 11:51:08','2015');insert into my_date VALUES('2015-09-28 11:50:36','2015-09-28','-11:50:54','2015-09-28 11:51:08','2015');-- -11insert into my_date VALUES('2015-09-28 11:50:36','2015-09-28','-211:50:54','2015-09-28 11:51:08','2015');-- -2 11insert into my_date VALUES('2015-09-28 11:50:36','2015-09-28','-2 11:50:54','2015-09-28 11:51:08','2015');-- -2 For the past two days #year use 69 identification -2069insert into my_date VALUES('2015-09-28 11:50:36','2015-09-28','11:50:54','2015-09-28 11:51:08','69');-- 69#year use 70 identification -1970insert into my_date VALUES('2015-09-28 11:50:36','2015-09-28','11:50:54','2015-09-28 11:51:08','70');-- 70

③ timestamp Field

By default, as long as the current record is updated , This field will be automatically updated to the current time .

update my_date set d1 = SYSDATE() where d5=69;select * from my_date

that MySQL Can I get the real timestamp ？ Certainly. ！

select UNIX_TIMESTAMP();

④ Test case

4.1 Query the current time

SELECT SYSDATE() from dual;

4.2 Insert the current time into the above types of columns

insert INTO `user` (name,number,date,datetime,timestamp,time,year)VALUES ('Loum',3,SYSDATE(),SYSDATE(),SYSDATE(),SYSDATE(),2016);

4.3 mysql in datetime Length digits of type

As shown below , Usually we MySQL Middle design datetime The type length defaults to 0：

`work_time` datetime(0) DEFAULT NULL COMMENT ' Collection time ',

At this time, the insertion time is often seen ：2020-08-29 12:52:16 Format . But if datetime(n) Medium n Not for 0 Well ？

`work_time` datetime(2) DEFAULT NULL COMMENT ' Collection time ',# datetime(n) Medium n The maximum value is 6`work_time` datetime(6) DEFAULT NULL COMMENT ' Collection time ',

At this moment in MySQL As shown below ：

2020-08-29 12:52:16.01
2020-08-29 12:52:16.014057

You will find that there is a decimal point at the end, and the digits after the decimal point will correspond to the corresponding digits – This is called nanosecond .

Summarized below ：

date : Only the date , don't have time ;

datetime： Have the time , With date ;

time： Only time , Accurate to minutes and seconds ;

timestamp： Time stamp , Accurate to minutes and seconds ;

year： year , Such as 2002, If it is written as 2002-01-15, Will be calculated , The insertion result is 1986

【2】 Format date time type ① DATE_FORMAT( ) function

have access to date_format( ) Function to convert time .

SELECT DATE_FORMAT(SYSDATE(),'%Y-%m-%d %H:%i:%s') from dual;

② date_format( ) Transformation format Format description

%a	Abbreviated week name
%b	Abbreviated month name
%c	month , The number
%D	Days of the month with English prefix
%d	Day of the month , The number (00-31)
%e	Day of the month , The number (0-31)
%f	Microsecond
%H	Hours (00-23)
%h	Hours (01-12)
%I	Hours (01-12)
%i	minute , The number (00-59)
%j	Days of (001-366)
%k	Hours (0-23)
%l	Hours (1-12)
%M	Month name
%m	month , The number (00-12)
%p	AM or PM
%r	Time ,12- Hours （hh:mm:ss AM or PM）
%S	second (00-59)
%s	second (00-59)
%T	Time , 24- Hours (hh:mm:ss)
%U	Zhou (00-53) Sunday is the first day of the week
%u	Zhou (00-53) Monday is the first day of the week
%V	Zhou (01-53) Sunday is the first day of the week , And %X Use
%v	Zhou (01-53) Monday is the first day of the week , And %x Use
%W	Week name
%w	Days of the week （0= Sunday , 6= Saturday ）
%X	year , Sunday is the first day of the week ,4 position , And %V Use
%x	year , Monday is the first day of the week ,4 position , And %v Use
%Y	year ,4 position
%y	year ,2 position

③ str_to_date() function

String conversion to date：

str_to_date('2016-12-15 16:48:40','%Y-%m-%d %H:%i:%S')

The above is personal experience , I hope I can give you a reference , I also hope you can support the software development network .