MySQL日期、时间、时间戳的获取与计算过程_Mysql

mysql日期处理

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获得时间

获得当前日期+时间（date + time）函数：now()
获得当前日期+时间（date + time）函数：sysdate()sysdate() 日期时间函数，一般情况下很少用到。
mysql 获得当前时间戳函数：current_timestamp, current_timestamp()

查询周数据

yearweek()

本周

select id, create_time
from user
where yearweek(date_format(modify_time, ‘%y-%m-%d')) = yearweek(now());

上周

select id, create_time
from user
where yearweek(date_format(create_time, ‘%y-%m-%d')) = yearweek(now()) - 1;

查询月数据

当前月份

select id, create_time
from user
where date_format(create_time, ‘%y-%m') = date_format(now(), ‘%y-%m')

距今六个月

select id, create_time
from user
where create_time between date_sub(now(), interval 6 month) and now();

上个月

select id, create_time
from user
where date_format(create_time, ‘%y-%m') = date_format(date_sub(curdate(), interval 1 month), ‘%y-%m')

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

日期时间计算

为日期增加一个时间间隔：date_add()

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

adddate(), addtime()函数，可以用 date_add() 来替代。

mysql> select date_add(@dt, interval ‘01:15:30' hour_second);

±-----------------------------------------------+
| date_add(@dt, interval ‘01:15:30' hour_second) |
±-----------------------------------------------+
| 2008-08-09 13:28:03 |
±-----------------------------------------------+

mysql> select date_add(@dt, interval ‘1 01:15:30' day_second);

±------------------------------------------------+
| date_add(@dt, interval ‘1 01:15:30' day_second) |
±------------------------------------------------+
| 2008-08-10 13:28:03 |
±------------------------------------------------+

为日期减去一个时间间隔：date_sub()

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

±---------------------------------------------------------------+
| date_sub(‘1998-01-01 00:00:00', interval ‘1 1:1:1' day_second) |
±---------------------------------------------------------------+
| 1997-12-30 22:58:59 |
±---------------------------------------------------------------+

date_sub() 日期时间函数和 date_add() 用法一致

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

timediff(time1,time2) 函数的两个参数类型必须相同。

mysql datediff(date1,date2)：两个日期相减 date1 - date2，返回天数。

select datediff(‘2008-08-08', ‘2008-08-01'); – 7
select datediff(‘2008-08-01', ‘2008-08-08'); – -7

mysql 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'); – 08:08:08
select timediff(‘08:08:08', ‘00:00:00'); – 08:08:08

时间戳（timestamp）转换、增、减函数：

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

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

后面的时间减去前面的时间

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。

日期时间转换

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)

select date_format(‘2008-08-08 22:23:01', ‘%y%m%d%h%i%s');

±---------------------------------------------------+
| date_format(‘2008-08-08 22:23:01', ‘%y%m%d%h%i%s') |
±---------------------------------------------------+
| 20080808222301 |
±---------------------------------------------------+

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。

str to date （字符串转换为日期）函数：str_to_date(str, format)

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

可以看到，str_to_date(str,format) 转换函数，可以把一些杂乱无章的字符串转换为日期格式。

（日期、天数）转换函数：to_days(date), from_days(days)

select to_days(‘0000-00-00'); – 0
select to_days(‘2008-08-08'); – 733627

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

select time_to_sec(‘01:00:05'); – 3605
select sec_to_time(3605); – ‘01:00:05'

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

select makedate(2001,31); – ‘2001-01-31'
select makedate(2001,32); – ‘2001-02-01'
select maketime(12,15,30); – ‘12:15:30'

（unix 时间戳、日期）转换函数

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'