What are the date and time types and formatting methods in MySQL

[1] Date and time types in MySQL

In MySQL, date, datetime, time, year and timestamp are commonly used time types

Data type	Occupied bytes	Minimum value	Maximum value	A zero value represents
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	Sometime in 2038	0000000000000000
time	3	-838:59: 59	838:59:59	00:00:00
year	1	1901	2155	0000

Detailed explanation

• ##datetime : Time date type, the format is YYYY-mm-dd HH:ii:ss , the representation range is from 1000 to 9999. But there is a zero value, 0000-00-00 00:00:00;

• date: Date is the date part of datetime;

• time: time (segment), between a specified interval, from - time to time (represented by negative time);

• timestamp: Timestamp, not a conventional timestamp (such as: 14253685), the range is '1970-01-01 00:00:00' to 2037. The format is YYYY-mm-dd HH:ii:ss,The format is completely consistent with datetime;

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

Two-digit year (00-69 means 2000-2069, 70-99 means 1970~1999). When the application only needs to record the year, year saves more space than date

SQL statement example

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 defaults to 4 digits, that is, YYYY; timestamp cannot be empty, and there is The default value is to refresh this data column when creating new records and modifying existing records.

Insert several pieces of data as follows and do a difference analysis on time:

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');-- -11
insert into my_date VALUES('2015-09-28 11:50:36','2015-09-28','-211:50:54','2015-09-28 11:51:08','2015');-- -2 11
insert 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过去两天
#year用69标识-2069
insert 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用70标识-1970
insert into my_date VALUES('2015-09-28 11:50:36','2015-09-28','11:50:54','2015-09-28 11:51:08','70');-- 70

timestamp field

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

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

So can MySQL get the real timestamp? sure!

select UNIX_TIMESTAMP();

Test Example

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 The length bit of datetime type in mysql The number

is as follows. Usually the length of the datetime type in our MySQL is designed to be 0 by default:

`work_time` datetime(0) DEFAULT NULL COMMENT '清收时间',

The common time format is usually 2020-08-29 12:52:16 , into which the current time is inserted. But what if n in datetime(n) is not 0?

`work_time` datetime(2) DEFAULT NULL COMMENT '清收时间',
# datetime(n)中的n最大值为6
`work_time` datetime(6) DEFAULT NULL COMMENT '清收时间',

At this time, it will be displayed as follows in MySQL:

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 numbers after the decimal point will correspond to the corresponding digits - this is called nanoseconds.

The summary is as follows:

• date : only date, no time;

• datetime: There is time and date;

• time: Only time, accurate to minutes and seconds;

• timestamp: timestamp, accurate to minutes and seconds;

• year: year, such as 2002, if written is 2002-01-15, calculation will be performed, and the insertion result is 1986

[2] Date and time type formatting

DATE_FORMAT( ) function

You can use the date_format() function to convert time.

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

date_format( ) 转换格式

格式	描述
%a	缩写星期名
%b	缩写月名
%c	月，数值
%D	带有英文前缀的月中的天
%d	月的天，数值(00-31)
%e	月的天，数值(0-31)
%f	微秒
%H	小时 (00-23)
%h	小时 (01-12)
%I	小时 (01-12)
%i	分钟，数值(00-59)
%j	年的天 (001-366)
%k	小时 (0-23)
%l	小时 (1-12)
%M	月名
%m	月，数值(00-12)
%p	AM 或 PM
%r	时间，12-小时（hh:mm:ss AM 或 PM）
%S	秒(00-59)
%s	秒(00-59)
%T	时间, 24-小时 (hh:mm:ss)
%U	周 (00-53) 星期日是一周的第一天
%u	周 (00-53) 星期一是一周的第一天
%V	周 (01-53) 星期日是一周的第一天，与 %X 使用
%v	周 (01-53) 星期一是一周的第一天，与 %x 使用
%W	星期名
%w	周的天 （0=星期日, 6=星期六）
%X	年，其中的星期日是周的第一天，4 位，与 %V 使用
%x	年，其中的星期一是周的第一天，4 位，与 %v 使用
%Y	年，4 位
%y	年，2 位

str_to_date()函数

字符串转换为date：

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

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