MySQL built-in date processing function

The following table lists the most important built-in date functions in MySQL:

function	Description
Now ()	Returns the current date and time
Curdate ()	Returns the current date
Curtime ()	Returns the current time
DATE ()	Extract date part of date or date/time expression
EXTRACT ()	Returns a separate part of the date/time Press
Date_add ()	Add a specified time interval to a date
Date_sub ()	Subtract a specified time interval from a date
DATEDIFF ()	Returns the number of days between two dates
Date_format ()	Display Date/time in a different format

Time difference function (Timestampdiff, DATEDIFF)

Need to use MySQL to calculate the time difference, using Timestampdiff, DATEDIFF, record the results of the experiment

--0Select DateDiff(now (), now ());--2Select DateDiff('2015-04-22 23:59:00','2015-04-20 00:00:00');--2Select DateDiff('2015-04-22 00:00:00','2015-04-20 23:59:00');--1SelectTimestampdiff ( Day,'2015-04-20 23:59:00','2015-04-22 00:00:00');--2SelectTimestampdiff ( Day,'2015-04-20 00:00:00','2015-04-22 00:00:00');--2SelectTimestampdiff ( Day,'2015-04-20 00:00:00','2015-04-22 12:00:00');--2SelectTimestampdiff ( Day,'2015-04-20 00:00:00','2015-04-22 23:59:00');-- inSelectTimestampdiff (HOUR,'2015-04-20 00:00:00','2015-04-22 23:00:00');--4260SelectTimestampdiff (MINUTE,'2015-04-20 00:00:00','2015-04-22 23:00:00');

Date conversion calculation functions (Date_add, Day, Date_format, str_to_date)

--use date and string conversions to calculate the first day of the month, the first day of the next monthSelectCurdate () as 'Current Date', Date_format (Curdate (),'%y-%m') as 'Current Month', Str_to_date (Concat (Date_format (Curdate (),'%y-%m'),'-01'),'%y-%m-%d') as 'the first day of the current month', Date_add (Str_to_date (Concat (Date_format) (Curdate (),'%y-%m'),'-01'),'%y-%m-%d'), Interval1 Month) as 'the first day of next month';--the last day of the current monthSelectLast_day (Curdate ());--the first day of next monthSelectDate_add (Last_day (Curdate ()), interval1  Day);--the day of the monthSelect  Day(Curdate ());--first day of the monthSelectDate_add (Curdate (), Interval1-( Day(Curdate ())) Day);

MySQL built-in date processing function