mysql 时间和日期函数学习
为了方便使用了比较智能的mysql客户端工具mycli，关于这个工具的介绍可以在另一篇文章（http://watchman110.blog.51cto.com/9194028/1687953）里了解！
1，now()函数，获得当前日期和时间
mysql root@localhost:(none)> SELECT NOW() +---------------------+ | NOW() | |---------------------| |2015-08-25 10:47:54 | +---------------------+
2，sysdate()函数，获得当前日期和时间
mysql root@localhost:(none)> SELECT SYSDATE() +---------------------+ | SYSDATE() | |---------------------| |2015-08-25 10:49:43 | +---------------------+
now()函数，和sysdate()函数作用类似，区别如下：now() 在执行开始时值就得到了， sysdate() 在函数执行时动态得到值
mysql root@localhost:(none)> SELECT NOW(),sleep(2),NOW() +---------------------+------------+---------------------+ | NOW() | sleep(2) | NOW() | |---------------------+------------+---------------------| | 2015-08-25 10:51:18 | 0 | 2015-08-25 10:51:18 | +---------------------+------------+---------------------+ mysql root@localhost:(none)> SELECT SYSDATE(),sleep(2),SYSDATE() +---------------------+------------+---------------------+ | SYSDATE() | sleep(2) | SYSDATE() | |---------------------+------------+---------------------| | 2015-08-25 10:52:01 | 0 | 2015-08-25 10:52:03 | +---------------------+------------+---------------------+
3，current_time(),curtime()函数，获得当前时间的函数
mysql root@localhost:(none)> SELECT CURRENT_TIME() +------------------+ | CURRENT_TIME() | |------------------| | 10:57:47 | +------------------+ mysql root@localhost:(none)> SELECT CURTIME() +-------------+ | CURTIME() | |-------------| | 10:57:55 | +-------------+
4，current_date(),curdate()函数，获得当前日期的函数
mysql root@localhost:(none)> SELECT CURRENT_DATE() +------------------+ | CURRENT_DATE() | |------------------| | 2015-08-25 | +------------------+ mysql root@localhost:(none)> SELECT CURDATE() +-------------+ | CURDATE() | |-------------| | 2015-08-25 | +-------------+
5,current_timestamp()函数，获得当前时间戳的函数
mysql root@localhost:(none)> SELECT CURRENT_TIMESTAMP() +-----------------------+ | CURRENT_TIMESTAMP() | |-----------------------| | 2015-08-25 11:00:21 | +-----------------------+
6，date_format(date,format)函数，日期格式转换函数，将日期转化为字符串形式
mysql root@localhost:(none)> SELECT curdate(),DATE_FORMAT(curdate(),'%Y%m%d'); +-------------+-----------------------------------+ | curdate() | DATE_FORMAT(curdate(),'%Y%m%d') | |-------------+-----------------------------------| | 2015-08-25 | 20150825 | +-------------+-----------------------------------+
7，time_format(time,format)函数，时间转换函数，将时间转化为字符串形式
mysql root@localhost:(none)> SELECT curtime(),time_format(curtime(),'%H%i%s') +-------------+-----------------------------------+ | curtime() | time_format(curtime(),'%H%i%s')| |-------------+----------------------------------- | | 11:15:17 | 111517 | +-------------+-----------------------------------+
上面函数的逆函数str_to_date()函数
mysql root@localhost:(none)> SELECT str_to_date('20150311','%Y%m%d')
+------------------------------------+
| str_to_date('20150311','%Y%m%d') |
|------------------------------------|
| 2015-03-11 |
+------------------------------------+
mysql root@localhost:(none)> SELECT str_to_date('121409','%H%i%s')
+----------------------------------+
| str_to_date('121409','%H%i%s') |
|----------------------------------|
| 12:14:09 |
+----------------------------------+
mysql root@localhost:(none)> SELECT str_to_date('20150903120000','%Y%m%d%H%i%s')
+------------------------------------------------+
| str_to_date('20150903120000','%Y%m%d%H%i%s') |
|------------------------------------------------|
| 2015-09-03 12:00:00 |
+------------------------------------------------+
8，unix_timestamp()函数，将时间转化为时间戳的函数
mysql root@localhost:(none)> SELECT unix_timestamp()
+--------------------+
| unix_timestamp() |
|--------------------|
| 1440474909 |
+--------------------+
mysql root@localhost:(none)> SELECT unix_timestamp('2015-09-03')
+--------------------------------+
| unix_timestamp('2015-09-03') |
|--------------------------------|
| 1441209600 |
+--------------------------------+
mysql root@localhost:(none)> SELECT unix_timestamp('2015-09-03 01:00:00')
+-----------------------------------------+
| unix_timestamp('2015-09-03 01:00:00') |
|-----------------------------------------|
| 1441213200 |
+-----------------------------------------+
9，from_unixtime(unix_timestamp)函数，将时间戳转换为时间字符串
mysql root@localhost:(none)> SELECT from_unixtime(1441209600)
+-----------------------------+
| from_unixtime(1441209600) |
|-----------------------------|
| 2015-09-03 00:00:00 |
+-----------------------------+
mysql root@localhost:(none)> SELECT from_unixtime(1441209600,'%Y%m%d %H:%i:%s')
+-----------------------------------------------+
| from_unixtime(1441209600,'%Y%m%d %H:%i:%s') |
|-----------------------------------------------|
| 20150903 00:00:00 |
+-----------------------------------------------+
10,date_add()函数，日期计算函数
mysql root@localhost:(none)> SELECT date_add(now(),interval 1 year)
+-----------------------------------+
| date_add(now(),interval 1 year) |
|-----------------------------------|
| 2016-08-25 13:53:16 |
+-----------------------------------+
mysql root@localhost:(none)> SELECT date_add(now(),interval 1 month)
+------------------------------------+
| date_add(now(),interval 1 month) |
|------------------------------------|
| 2015-09-25 13:54:38 |
+------------------------------------+
mysql root@localhost:(none)> SELECT date_add(now(),interval 1 week)
mysql root@localhost:(none)> SELECT date_add(now(),interval 1 day)
mysql root@localhost:(none)> SELECT date_add(now(),interval 1 hour)
mysql root@localhost:(none)> SELECT date_add(now(),interval 1 minute)
mysql root@localhost:(none)> SELECT date_add(now(),interval 1 second)
同理 -1 指的是一年/月/日/天/时/分/秒以前
mysql root@localhost:(none)> SELECT date_add(now(),interval -1 year)
+------------------------------------+
| date_add(now(),interval -1 year) |
|------------------------------------|
| 2014-08-25 13:57:46 |
+------------------------------------+
11,datediff(date1,date2),日期相减函数，返回的是天数
mysql root@localhost:(none)> SELECT datediff('2015-09-03','2015--8-25')
+---------------------------------------+
| datediff('2015-09-03','2015--8-25') |
|---------------------------------------|
| 9 |
+---------------------------------------+
mysql root@localhost:(none)> SELECT datediff('2015--8-25','2015-09-03')
+---------------------------------------+
| datediff('2015--8-25','2015-09-03') |
|---------------------------------------|
| -9 |
+---------------------------------------+
12,timediff(time1,time2)，时间相减函数，返回的是时间差值
mysql root@localhost:(none)> SELECT timediff('12:37:33','12:35:32')
+-----------------------------------+
| timediff('12:37:33','12:35:32') |
|-----------------------------------|
| 0:02:01 |
+-----------------------------------+
mysql root@localhost:(none)> SELECT timediff('12:35:32','12:37:33')
+-----------------------------------+
| timediff('12:35:32','12:37:33') |
|-----------------------------------|
| -1 day, 23:57:59 |
+-----------------------------------+
13，timestamp()时间戳转换，增，减函数
mysql root@localhost:(none)> select timestamp('2013-08-25');
+---------------------------+
| timestamp('2013-08-25') |
|---------------------------|
| 2013-08-25 00:00:00 |
+---------------------------+
mysql root@localhost:(none)> select timestamp('2013-08-25','01:00:00');
+--------------------------------------+
| timestamp('2013-08-25','01:00:00') |
|--------------------------------------|
| 2013-08-25 01:00:00 |
+--------------------------------------+
14，timestampadd()，函数类似于 date_add()，强大于date_add()
mysql root@localhost:(none)> select timestampdiff(year,'2013-01-01','2015-01-01')
+-------------------------------------------------+
| timestampdiff(year,'2013-01-01','2015-01-01') |
|-------------------------------------------------|
| 2 |
+-------------------------------------------------+
mysql root@localhost:(none)> select timestampdiff(month,'2013-01-01','2015-03-01')
+--------------------------------------------------+
| timestampdiff(month,'2013-01-01','2015-03-01') |
|--------------------------------------------------|
| 26 |
+--------------------------------------------------+
mysql root@localhost:(none)> select timestampdiff(day,'2013-01-01','2015-03-01')
+------------------------------------------------+
| timestampdiff(day,'2013-01-01','2015-03-01') |
|------------------------------------------------|
| 789 |
+------------------------------------------------+
mysql root@localhost:(none)> select timestampdiff(hour,'2013-01-01','2015-03-01')
+-------------------------------------------------+
| timestampdiff(hour,'2013-01-01','2015-03-01') |
|-------------------------------------------------|
| 18936 |
+-------------------------------------------------+
mysql root@localhost:(none)> select timestampdiff(second,'2013-01-01','2015-03-01')
+---------------------------------------------------+
| timestampdiff(second,'2013-01-01','2015-03-01') |
|---------------------------------------------------|
| 68169600 |
+---------------------------------------------------+