###My SQL Date相关函数

###My SQL Date相关函数

#获得当前日期时间
select now();

#date_format(date,format)
 select date_format('2008-08-08 22:23:01', '%Y%m%d%H%i%s');

#str_to_date(str, format)

select str_to_date('08/09/2008', '%m/%d/%Y'); -- --
select str_to_date('08/09/08' , '%m/%d/%y'); -- --
select str_to_date('08.09.2008', '%m.%d.%Y'); -- --
select str_to_date('08:09:30', '%h:%i:%s'); -- ::
select str_to_date('08.09.2008 08:09:30', '%m.%d.%Y %h:%i:%s'); -- -- ::

#makdedate(year,dayofyear), maketime(hour,minute,second)
select makedate(,); -- '2001-01-31'
select makedate(,); -- '2001-02-01'
select maketime(,,); -- '12:15:30'

select unix_timestamp(); --
select from_unixtime(); -- '2008-08-09 21:53:47'

#date_add()
set @dt = now();
select date_add(@dt, interval  day); -- add  day
select date_add(@dt, interval  hour); -- add  hour
select date_add(@dt, interval  minute); -- ...
select date_add(@dt, interval  second);
select date_add(@dt, interval  microsecond);
select date_add(@dt, interval  week);
select date_add(@dt, interval  month);
select date_add(@dt, interval  quarter);
select date_add(@dt, interval  year);

#addtime
set @dt = '2008-08-09 12:12:33';
select date_add(@dt, interval '01:15:30' hour_second);

#date_sub
select date_sub('1998-01-01 00:00:00', interval '1 1:1:1' day_second);

#datediff(date1,date2)：两个日期相减 date1 - date2，返回天数。
select datediff('2008-08-08', '2008-08-01'); --
select datediff('2008-08-01', '2008-08-08'); -- -

 #timediff(time1,time2)：两个日期相减 time1 - time2，返回 time 差值。
select timediff('2008-08-08 08:08:08', '2008-08-08 00:00:00'); -- ::
select timediff('08:08:08', '00:00:00'); -- ::

#timestampadd() 函数类似于 date_add()。
select timestampdiff(year,'2002-05-01','2001-01-01'); -- -
select timestampdiff(day ,'2002-05-01','2001-01-01'); -- -
select timestampdiff(hour,'2008-08-08 12:00:00','2008-08-08 00:00:00'); -- -

#https://www.cnblogs.com/php12-cn/p/8882221.html