Summary of date and time types and formatting methods in MySQL

This article brings you relevant knowledge about mysql. It mainly introduces the date and time types and formatting methods in MySQL. Several commonly used time types in MySQL are: date, datetime , time, year, timestamp, let’s take a look at it, I hope it will be helpful to everyone.

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[1] Date and time types in MySQL

MySQL Several commonly used time types are: date, datetime, time, year, timestamp

Detailed explanation

• datetime : Time date type, the format is YYYY-mm-dd HH: ii:ss, the 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 time Stamp (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, the range of yyyy is 1901-2155 , 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 be automatically updated 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',

At this time, the insertion time is usually what we often see: 2020-08- 29 12:52:16 format. 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: With time and date;
• time: Only time, accurate to minutes and seconds;
• timestamp: Timestamp, accurate to minutes Seconds;
• year: year, such as 2002, if written as 2002-01-15, calculation will be performed, and the inserted result will be 1986

[2 】Date 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

 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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