获得当前日期+时间(date + time)函数:now()
mysql> select now();+---------------------+| now() |+---------------------+| -08-08 22:20:46 |+---------------------+
获得当前日期+时间(date + time)函数:sysdate()
sysdate() 日期时间函数跟 now() 类似,不同之处在于:now() 在执行开始时值就得到了, sysdate() 在函数执行时动态得到值。看下面的例子就明白了:
mysql> select now(), sleep(3), now();+---------------------+----------+---------------------+| now() | sleep(3) | now() |+---------------------+----------+---------------------+| -08-08 22:28:21 | 0 | -08-08 22:28:21 |+---------------------+----------+---------------------+
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()
mysql> select current_timestamp, current_timestamp();+---------------------+---------------------+| current_timestamp | current_timestamp() |+---------------------+---------------------+| -08-09 23:22:24 | -08-09 23:22:24 |+---------------------+---------------------+
MySQL 日期转换函数、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("-08-08 22:23:01", "%Y%m%d%H%i%s");+----------------------------------------------------+| date_format("-08-08 22:23:01", "%Y%m%d%H%i%s") |+----------------------------------------------------+| 0808222301 |+----------------------------------------------------+
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 Str to Date (字符串转换为日期)函数:str_to_date(str, format)
select str_to_date("08/09/", "%m/%d/%Y"); -- -08-09select str_to_date("08/09/08" , "%m/%d/%y"); -- -08-09select str_to_date("08.09.", "%m.%d.%Y"); -- -08-09select str_to_date("08:09:30", "%h:%i:%s"); -- 08:09:30select str_to_date("08.09. 08:09:30", "%m.%d.%Y %h:%i:%s"); -- -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。另外,它也可以转换为时间。“format” 可以参看 MySQL 手册。
MySQL (日期、天数)转换函数:to_days(date), from_days(days)
select to_days("0000-00-00"); -- 0select to_days("-08-08"); -- 733627
MySQL (时间、秒)转换函数:time_to_sec(time), sec_to_time(seconds)
select time_to_sec("01:00:05"); --3605select sec_to_time(3605); -- "01:00:05"
MySQL 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"
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)
下面是示例:
select unix_timestamp(); -- 1218290027select unix_timestamp("-08-08"); -- 1218124800select unix_timestamp("-08-08 12:30:00"); -- 1218169800select from_unixtime(1218290027); -- "-08-09 21:53:47"select from_unixtime(1218124800); -- "-08-08 00:00:00"select from_unixtime(1218169800); -- "-08-08 12:30:00"select from_unixtime(1218169800, "%Y %D %M %h:%i:%s %x"); -- " 8th August 12:30:00 "
MySQL 日期时间计算函数
MySQL 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 dayselect date_add(@dt, interval 1 hour); -- add 1 hourselect 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
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 = "-08-09 12:12:33";mysql>mysql> select date_add(@dt, interval "01:15:30" hour_second);+------------------------------------------------+| date_add(@dt, interval "01:15:30" hour_second) |+------------------------------------------------+| -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) |+-------------------------------------------------+| -08-10 13:28:03 |+-------------------------------------------------+
MySQL 为日期减去一个时间间隔:date_sub()
mysql> 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 |+----------------------------------------------------------------+
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。select datediff("-08-08", "-08-01"); -- 7select datediff("-08-01", "-08-08"); -- -7
MySQL timediff(time1,time2):两个日期相减 time1 - time2,返回 time 差值。
select timediff("-08-08 08:08:08", "-08-08 00:00:00"); -- 08:08:08select timediff("08:08:08", "00:00:00"); -- 08:08:08
注意:timediff(time1,time2) 函数的两个参数类型必须相同。
MySQL 时间戳(timestamp)转换、增、减函数:
timestamp(date) -- date to timestamptimestamp(dt,time) -- dt + timetimestampadd(unit,interval,datetime_expr) --timestampdiff(unit,datetime_expr1,datetime_expr2) --
请看示例部分:
select timestamp("-08-08"); -- -08-08 00:00:00select timestamp("-08-08 08:00:00", "01:01:01"); -- -08-08 09:01:01select timestamp("-08-08 08:00:00", "10 01:01:01"); -- -08-18 09:01:01select timestampadd(day, 1, "-08-08 08:00:00"); -- -08-09 08:00:00select date_add("-08-08 08:00:00", interval 1 day); -- -08-09 08:00:00MySQL timestampadd() 函数类似于 date_add()。select timestampdiff(year,"2002-05-01","2001-01-01"); -- -1select timestampdiff(day ,"2002-05-01","2001-01-01"); -- -485select timestampdiff(hour,"-08-08 12:00:00","-08-08 00:00:00"); -- -12select datediff("-08-08 12:00:00", "-08-01 00:00:00"); -- 7
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。
MySQL 时区(timezone)转换函数
convert_tz(dt,from_tz,to_tz)select convert_tz("-08-08 12:00:00", "+08:00", "+00:00"); -- -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("-08-08 12:00:00", interval -8 hour); -- -08-08 04:00:00select date_sub("-08-08 12:00:00", interval 8 hour); -- -08-08 04:00:00select timestampadd(hour, -8, "-08-08 12:00:00"); -- -08-08 04:00:00
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