Mysql's STR_TO_DATE and DATE_FORMAT functions

1. Available backgrounds:

1. DATE_FORMAT: Convert the date data in the database to the String type we want

2. STR_TO_DATE: It is necessary to convert the string in the specified time format to a value of type DATETIME according to the provided display format

2. Grammar:

1. date_format(date, format); Among them, date is the date data that needs to be converted, and format defines the conversion format.

2. str_to_date(str, format); where str is the string data to be converted, and format defines the conversion format.

Three, format format:

Format	describe
%a	abbreviated day of the week
%b	abbreviated month name
%c	month, value
%D	day of month with english prefix
%d	Day of the month, value (00-31)
%e	Day of the month, value (0-31)
%f	microsecond
%H	hour (00-23)
%h	hour (01-12)
%I	hour (01-12)
%i	minute, value (00-59)
%j	Day of the year (001-366)
%k	hour(0-23)
%l	hours (1-12)
%M	month name
%m	month, value (00-12)
%p	AM or PM
%r	Time, 12-hour (hh:mm:ss AM or PM)
%S	seconds (00-59)
%s	seconds (00-59)
%T	Time, 24-hour (hh:mm:ss)
%U	Week (00-53) Sunday is the first day of the week
%u	Week (00-53) Monday is the first day of the week
%V	Week (01-53) Sunday is the first day of the week, used with %X
%v	Week (01-53) Monday is the first day of the week, use with %x
%W	week name
%w	Day of the week (0=Sunday, 6=Saturday)
%X	Year, where Sunday is the first day of the week, 4 digits, used with %V
%x	Year, where Monday is the first day of the week, 4 digits, used with %v
%Y	year, 4 digits
%y	year, 2 digits

4. Example:

DATE_FORMAT:

SELECT DATE_FORMAT(NOW(),'%b %d %Y %h:%i %p');
SELECT DATE_FORMAT(NOW(),'%m-%d-%Y');
SELECT DATE_FORMAT(NOW(),'%d %b %y');
SELECT DATE_FORMAT(NOW(),'%d %b %Y %T:%f');

结果：
Oct 14 2021 04:18 PM
10-14-2021
14 Oct 21
14 Oct 2021 16:18:52:000000

STR_TO_DATE:

SELECT STR_TO_DATE('15:00:00', '%H:%i:%s');
SELECT STR_TO_DATE('2021-10-14 15:00:00', '%Y-%m-%d %H:%i:%s');

结果：
15:00:00
2021-10-14 15:00:00

5. Matters needing attention

STR_TO_DATE
中str的格式需要和format的格式保持一致；例如 str_to_date(‘2021-10-14 15:00:00’，‘%Y-%m-%d %H:%i:%s’),若是前后不一致则会报错。
示例：