日期函数、时间函数总结

一、获取mysql当前时间

获取当前日期+时间（date+time）函数：now();

mysql> select localtime();
mysql> select now();
+---------------------+
| now()               |
+---------------------+
| 2018-09-16 19:26:55 |
+---------------------+
1 row in set (0.00 sec)

mysql> select current_timestamp();
+---------------------+
| current_timestamp() |
+---------------------+
| 2018-09-16 19:27:21 |
+---------------------+
1 row in set (0.00 sec)

二、MySQL 日期转换函数和时间转换函数

MySQL Date/Time to Str（日期/时间转换为字符串）函数：

date_format(date,format), time_format(time,format)
mysql> select date_format('2018-09-16','%Y/%m/%d');
+--------------------------------------+
| date_format('2018-09-16','%Y/%m/%d') |
+--------------------------------------+
| 2018/09/16                           |
+--------------------------------------+
1 row in set (0.00 sec)
mysql> select date_format('2018-09-16 19:32:20','%Y%m%d%H%i%s');
+---------------------------------------------------+
| date_format('2018-09-16 19:32:20','%Y%m%d%H%i%s') |
+---------------------------------------------------+
| 20180916193220                                    |
+---------------------------------------------------+
1 row in set (0.00 sec)

提示：如果为大写M,则为英文9月，大写D则为英文16th,大写H则可以正常显示12点以后的数字

mysql> select date_format('2018-09-16 19:32:20','%Y%M%D%H%i%s');
+---------------------------------------------------+
| date_format('2018-09-16 19:32:20','%Y%M%D%H%i%s') |
+---------------------------------------------------+
| 2018September16th193220                           |
+---------------------------------------------------+
1 row in set (0.00 sec)


mysql> select time_format('18:23:20','%H/%i/%s');
+------------------------------------+
| time_format('18:23:20','%H/%i/%s') |
+------------------------------------+
| 18/23/20                           |
+------------------------------------+
1 row in set (0.00 sec)

mysql> select time_format('18:23:20','%H-%i-%s');
+------------------------------------+
| time_format('18:23:20','%H-%i-%s') |
+------------------------------------+
| 18-23-20                           |
+------------------------------------+
1 row in set (0.00 sec)

MySQL 日期、时间转换函数： date_format(date,format), time_format(time,format) 能够把一个日期/时间转换成各种各样的字符串格式。它是 str_to_date(str,format) 函数的 一个逆转换

mysql> select str_to_date('16/09/2018', '%d/%m/%Y');
+---------------------------------------+
| str_to_date('16/09/2018', '%d/%m/%Y') |
+---------------------------------------+
| 2018-09-16                            |
+---------------------------------------+
1 row in set (0.00 sec)
mysql> select str_to_date('16.09.2018', '%d.%m.%Y');
+---------------------------------------+
| str_to_date('16.09.2018', '%d.%m.%Y') |
+---------------------------------------+
| 2018-09-16                            |
+---------------------------------------+
1 row in set (0.00 sec)

MySQL （时间、秒）转换函数：time_to_sec(time), sec_to_time(seconds)

mysql> select time_to_sec('01:00:05');
+-------------------------+
| time_to_sec('01:00:05') |
+-------------------------+
|                    3605 |
+-------------------------+
1 row in set (0.00 sec)

mysql> select sec_to_time('3605');
+---------------------+
| sec_to_time('3605') |
+---------------------+
| 01:00:05.000000     |
+---------------------+
1 row in set (0.02 sec)

mysql> 

MySQL 拼凑日期、时间函数：makedate(year,dayofyear), maketime(hour,minute,second)

mysql> select makedate(2018,31);
+-------------------+
| makedate(2018,31) |
+-------------------+
| 2018-01-31        |
+-------------------+
1 row in set (0.00 sec)

mysql> select makedate(2018,32);
+-------------------+
| makedate(2018,32) |
+-------------------+
| 2018-02-01        |
+-------------------+
1 row in set (0.00 sec)


mysql> select makedate(2018,259);
+--------------------+
| makedate(2018,259) |
+--------------------+
| 2018-09-16         |
+--------------------+
1 row in set (0.00 sec)

mysql> 
mysql> select maketime(12,15,30);
+--------------------+
| maketime(12,15,30) |
+--------------------+
| 12:15:30           |
+--------------------+
1 row in set (0.00 sec)

MySQL （Unix 时间戳、日期）转换函数

unix_timestamp(),
unix_timestamp(date),
from_unixtime(unix_timestamp),
from_unixtime(unix_timestamp,format)

select unix_timestamp(); -- 1218290027
select unix_timestamp('2008-08-08'); -- 1218124800
select unix_timestamp('2008-08-08 12:30:00'); -- 1218169800

select from_unixtime(1218290027); -- '2008-08-09 21:53:47'
select from_unixtime(1218124800); -- '2008-08-08 00:00:00'
select from_unixtime(1218169800); -- '2008-08-08 12:30:00'

select from_unixtime(1218169800, '%Y %D %M %h:%i:%s %x'); -- '2008 8th August 12:30:00 2008'

三、MySQL 日期时间计算函数:

date_add() MySQL日期增加函数：

date_add(curdate(), interval 1 day); ##curdate()代表当前日期，interval + num代表增加num 天，interval - num代表减去num 天

mysql> select date_add(curdate(), interval 1 day);
+-------------------------------------+
| date_add(curdate(), interval 1 day) |
+-------------------------------------+
| 2018-09-17                          |
+-------------------------------------+
1 row in set (0.00 sec)

select date_add(curtime(), interval -1 hour); ##curtime()代表当前时间； interval -1 hour代表减去1小时。

mysql> select date_add(curtime(), interval -1 hour);
+---------------------------------------+
| date_add(curtime(), interval -1 hour) |
+---------------------------------------+
| 19:14:10                              |
+---------------------------------------+
1 row in set (0.00 sec)

mysql> select date_add(curtime(), interval +1 hour);
+---------------------------------------+
| date_add(curtime(), interval +1 hour) |
+---------------------------------------+
| 21:14:31                              |
+---------------------------------------+
1 row in set (0.00 sec)

MySQL 为日期增加一个时间间隔：

set @dt = now();

select date_add(@dt, interval 1 day); -- add 1 day
select date_add(@dt, interval 1 hour); -- add 1 hour
select date_add(@dt, interval 1 minute); -- ...
select date_add(@dt, interval 1 second);
select date_add(@dt, interval 1 microsecond);
select date_add(@dt, interval 1 week);
select date_add(@dt, interval 1 month);
select date_add(@dt, interval 1 quarter);
select date_add(@dt, interval 1 year);
select date_add(@dt, interval -1 day); -- sub 1 day

选取日期时间的各个部分：日期、时间、年、季度、月、日、小时、分钟、秒、微秒

set @dt = '20018-09-10 07:15:30.123456';

select date(@dt); -- 20018-09-10
select time(@dt); -- 07:15:30.123456
select year(@dt); -- 2008
select quarter(@dt); -- 3
select month(@dt); -- 9
select week(@dt); -- 36
select day(@dt); -- 10
select hour(@dt); -- 7
select minute(@dt); -- 15
select second(@dt); -- 30
select microsecond(@dt); -- 123456

MySQL adddate(), addtime()函数，可以用 date_add() 来替代。下面是 date_add() 实现 addtime() 功能示例：

mysql> set @dt = '2018-09-16 20:12:33';
mysql> select date_add(@dt, interval '01:15:30' hour_second);
+------------------------------------------------+
| date_add(@dt, interval '01:15:30' hour_second) |
+------------------------------------------------+
| 2018-09-16 21:28:03                            |
+------------------------------------------------+
1 row in set (0.00 sec)

mysql> 

mysql>  select date_add(@dt, interval '1 01:15:30' day_second);
+-------------------------------------------------+
| date_add(@dt, interval '1 01:15:30' day_second) |
+-------------------------------------------------+
| 2018-09-17 21:28:03                             |
+-------------------------------------------------+
1 row in set (0.00 sec)

mysql> 

date_sub()mysql日期减去函数： MySQL 为日期减去一个时间间隔：date_sub() 当前日期减去一天

mysql> select date_sub(curdate(),interval 1 day);
+------------------------------------+
| date_sub(curdate(),interval 1 day) |
+------------------------------------+
| 2018-09-15                         |
+------------------------------------+
1 row in set (0.00 sec)

当前日期增加一天：

mysql> select date_sub(curdate(),interval -1 day);
+-------------------------------------+
| date_sub(curdate(),interval -1 day) |
+-------------------------------------+
| 2018-09-17                          |
+-------------------------------------+
1 row in set (0.00 sec)

MySQL为日期2018-09-16 00:00:00减去一个时间间隔

mysql> select date_sub('2018-09-16 00:00:00', interval '1 1:1:1' day_second);
+----------------------------------------------------------------+
| date_sub('2018-09-16 00:00:00', interval '1 1:1:1' day_second) |
+----------------------------------------------------------------+
| 2018-09-14 22:58:59                                            |
+----------------------------------------------------------------+
1 row in set (0.00 sec)

提示： MySQL date_sub() 日期时间函数 和 date_add() 用法一致，不再赘述。

MySQL 日期、时间相减函数：datediff(date1,date2), timediff(time1,time2)

MySQL datediff(date1,date2)：两个日期相减 date1 - date2，返回天数。
mysql> select datediff('2018-09-16','2018-08-16');
+-------------------------------------+
| datediff('2018-09-16','2018-08-16') |
+-------------------------------------+
|                                  31 |
+-------------------------------------+
1 row in set (0.00 sec)

MySQL timediff(time1,time2)：两个日期相减 time1 - time2，返回 time 差值。

mysql> select timediff('20:49:30','20:48:10');
+---------------------------------+
| timediff('20:49:30','20:48:10') |
+---------------------------------+
| 00:01:20                        |
+---------------------------------+
1 row in set (0.00 sec)


mysql> select timediff('2018-09-16 20:49:30','2018-09-15 20:48:10');
+-------------------------------------------------------+
| timediff('2018-09-16 20:49:30','2018-09-15 20:48:10') |
+-------------------------------------------------------+
| 24:01:20                                              |
+-------------------------------------------------------+
1 row in set (0.00 sec)

注意：timediff(time1,time2) 函数的两个参数类型必须相同。

四、MySQL 时间戳（timestamp）转换、增、减函数：

timestamp(date) -- date to timestamp
timestamp(dt,time) -- dt + time
timestampadd(unit,interval,datetime_expr) --
timestampdiff(unit,datetime_expr1,datetime_expr2) --

请看示例部分：

select timestamp('2008-08-08'); -- 2008-08-08 00:00:00
select timestamp('2008-08-08 08:00:00', '01:01:01'); -- 2008-08-08 09:01:01
select timestamp('2008-08-08 08:00:00', '10 01:01:01'); -- 2008-08-18 09:01:01

select timestampadd(day, 1, '2008-08-08 08:00:00'); -- 2008-08-09 08:00:00
select date_add('2008-08-08 08:00:00', interval 1 day); -- 2008-08-09 08:00:00

MySQL timestampadd() 函数类似于 date_add()。
select timestampdiff(year,'2002-05-01','2001-01-01'); -- -1
select timestampdiff(day ,'2002-05-01','2001-01-01'); -- -485
select timestampdiff(hour,'2008-08-08 12:00:00','2008-08-08 00:00:00'); -- -12

select datediff('2008-08-08 12:00:00', '2008-08-01 00:00:00'); -- 7

提示：MySQL timestampdiff() 函数就比 datediff() 功能强多了，datediff() 只能计算两个日期（date）之间相差的天数。

五、MySQL 时区timezone转换函数

convert_tz(dt,from_tz,to_tz)

select convert_tz('2008-08-08 12:00:00', '+08:00', '+00:00'); -- 2008-08-08 04:00:00
时区转换也可以通过 date_add, date_sub, timestampadd 来实现。

select date_add('2008-08-08 12:00:00', interval -8 hour); -- 2008-08-08 04:00:00
select date_sub('2008-08-08 12:00:00', interval 8 hour); -- 2008-08-08 04:00:00
select timestampadd(hour, -8, '2008-08-08 12:00:00'); -- 2008-08-08 04:00:00