mysql date function

MySQL common date and time functions

date and time functions

Possible needs:

　　What is the current time, today is the day of the week in the next month, the total income of the 3 days before the current date is counted...

The above requirements need to be implemented using date and time functions:

There are three time zone settings in MySQL server:

　　①System time zone - saved in the system variable system_time_zone

　　②Server time zone - saved in the global system variable global.time_zone

　　③ The time zone of each client connection - saved in the session variable session.time_zone

Notice:

　　The setting of the client time zone will affect the display of the return value of some date functions, such as now(), curtime(), curdate(), and also the display of the timestamp column value.

　　By default, the time zone of the client and server is the same, and its value is SYSTEM, which means the system time zone is used.

1. NOW([fsp]): Returns the current date and time of the server (fsp specifies the precision of fractional seconds, with a value of 0–6)

Format:

　　'YYYY-MM-DD HH:MM:SS' or 'YYYYMMDDHHMMSS'

The display format of copy code
now() is 'YYYY-MM-DD HH:MM:SS'
The display format of now()+0 is 'YYYYMMDDHHMMSS'
mysql> select now();
+——————+
| now() |
+——————+
| 2017-03-24 13:53:34 |
+——————+

mysql> select now()+0;
+————-+
| now()+0 |
+————-+
| 20170324135428 |
+————-+
　mysql> select now(6) ; //Specify the precision of fractional seconds
　+—————————-+
　| now(6) |
　+—————————-+
　| 2017-04-19 19:55:46.658198 |
　+—————————-+

Synonyms for the now() function are: CURRENT_TIMESTAMP, CURRENT_TIMESTAMP(), LOCALTIMESTAMP
, LOCALTIMESTAMP(), LOCALTIME, LOCALTIME()

Notice:

　　SYSDATE( ): Returns the current date and time of the server

The difference from now: (usually use NOW instead of SYSDATE)

　　①SYSDATE() returns the time when the function is executed

　　②now() returns the time when the statement was executed

复制代码
mysql> select now(),sleep(2),now();
+———————+———-+———————+
| now() | sleep(2) | now() |
+———————+———-+———————+
| 2017-04-19 20:01:39 | 0 | 2017-04-19 20:01:39 |
+———————+———-+———————+
1 row in set (2.00 sec)

mysql> select sysdate(),sleep(2),sysdate();
+———————+———-+———————+
| sysdate() | sleep(2) | sysdate() |
+———————+———-+———————+
| 2017-04-19 20:02:01 | 0 | 2017-04-19 20:02:03 |
+———————+———-+———————+
1 row in set (2.05 sec)
复制代码

2. CURTIME([fsp]): Returns the current time, including only hours, minutes and seconds (fsp specifies the precision of fractional seconds, with a value of 0–6)

Format:

　　'YYYY-MM-DD HH:MM:SS' or 'YYYYMMDDHHMMSS'

Copy code
mysql> select curtime(),curtime(2);
+——–+————-+
| curtime() | curtime(2) |
+——–+————-+
| 14 :35:23 | 14:35:23.90 |
+——–+————-+
Copy code
Synonyms are: CURRENT_TIME , CURRENT_TIME()

3. CURDATE(): Returns the current date, including only the year, month and day

Format:

　　'YYYY-MM-DD' or 'YYYYMMDD'

Copy code
mysql> select curdate(),curdate()+2;
+————+————-+
| curdate() | curdate()+2 |
+————+————-+
| 2017-03-24 | 20170326 |
+————+————-+

mysql> select curdate(),curdate()+0;
+————+————-+
| curdate() | curdate()+0 |
+————+————-+
| 2017 -03-24 | 20170324 |
+————+————-+
Copy code
Synonyms are: CURRENT_DATE, CURRENT_DATE()

4. TIMEDIFF(expr1, expr2): Returns the time difference between two dates (expr1 − expr2 ) (the two parameter types must be the same)

Copy code
mysql> select timediff('18:32:59','60000');
+————————+
| timediff('18:32:59','60000') |
+— —————————+
| 12:32:59 |
+—————————+

mysql> select timediff('18:32:59','2017-1-1 60000');
+————————————+
| timediff('18:32:59',' 2017-1-1 60000') |
+————————————+
| NULL |
+————————————+
Copy Code

DATEDIFF(expr1, expr2): Returns the number of days between two dates minus (expr1 − expr2 )

Copy code
mysql> select datediff('2017-3-24 18:32:59','2016-9-1');
+——————————————-+
| datediff(' 2017-3-24 18:32:59','2016-9-1') |
+——————————————-+
| 204 |
+———————— ——————-+
copy code

5. Date and time operation function: add (add) or subtract (sub) a time interval value expr to the given date respectively

Format:

　　DATE_ADD(date, INTERVAL expr unit);

　　DATE_SUB(date, INTERVAL expr unit);

interval is the interval type keyword

expr is an expression corresponding to the following type

unit is the unit (interval type) (20) of the time interval, as follows:

HOUR

Hour

MINUTE

Minute

SECOND

Second

MICROSECOND

millisecond

YEAR

year

MONTH

moon

DAY

day

WEEK

week

QUARTER

season

YEAR_MONTH

year and month

DAY_HOUR

day and hour

DAY_MINUTE

day and minute

DAY_ SECOND

day and second

HOUR_MINUTE

hours and minutes

HOUR_SECOND

hours and seconds

MINUTE_SECOND

minutes and seconds

Copy code
mysql> select now(),date_add(now(),interval 1 day); #Add one day
+——————+———————————–+
| now() | date_add (now(),interval 1 day) |
+——————+—————————–+
| 2017-03-24 14:53:08 | 2017-03-25 14: 53:08 |
+————————+———————————–+

mysql> SELECT date_sub('2005-01-01 00:00:00',INTERVAL '1 1:1:1' DAY_SECOND); #Subtract 1 day, 1 hour, 1 minute and 1 second
+————————— ————————————+
| date_sub('2005-01-01 00:00:00',INTERVAL '1 1:1:1' DAY_SECOND) |
+———————— ————————————+
| 2004-12-30 22:58:59 |
+—————————————————————+
Copy code

You can also write expressions to add and subtract dates without using functions:

　　date + INTERVAL expr unit

　　date - INTERVAL expr unit

Copy code
mysql> SELECT '2008-12-31 23:59:59' + INTERVAL 1 SECOND;
+———————————————-+
| '2008-12-31 23:59: 59' + INTERVAL 1 SECOND |
+———————————————-+
| 2009-01-01 00:00:00 |
+—————————————— —-+
1 row in set (0.00 sec)

mysql> SELECT '2005-01-01' - INTERVAL 1 SECOND;
+———————————-+
| '2005-01-01' - INTERVAL 1 SECOND |
+———————— ————-+
| 2004-12-31 23:59:59 |
+———————————-+
1 row in set (0.00 sec
)

6. Select each part of the date and time: date, time, year, quarter, month, day, hour, minute, second, microsecond (commonly used)

SELECT now(),date(now()); – 日期

SELECT now(),time(now()); - time

SELECT now(),year(now()); – 年

SELECT now(),quarter(now()); – quarter

SELECT now(),month(now()); – 月

SELECT now(),week(now()); – 周

SELECT now(),day(now()); – 日

SELECT now(),hour(now()); – 小时

SELECT now(),minute(now()); – 分钟

SELECT now(),second(now()); – 秒

SELECT now(),microsecond(now()); – 微秒

EXTRACT (unit FROM date): extract a single part or combination from a date

SELECT now(),extract(YEAR FROM now()); – 年

SELECT now(),extract(QUARTER FROM now()); – 季度

SELECT now(),extract(MONTH FROM now()); – 月

SELECT now(),extract(WEEK FROM now()); – 周

SELECT now(),extract(DAY FROM now()); – 日

SELECT now(),extract(HOUR FROM now()); – 小时

SELECT now(),extract(MINUTE FROM now()); – 分钟

SELECT now(),extract(SECOND FROM now()); – 秒

SELECT now(),extract(YEAR_MONTH FROM now()); – 年月

SELECT now(),extract(HOUR_MINUTE FROM now()); – 时分

7. Personalized display time and date

　　dayofweek(date)

　　dayofmonth(date)

　　dayofyear(date)

Returns the day of the week, January, and year, respectively

复制代码
mysql> SELECT now(),dayofweek(now());
+———————+——————+
| now() | dayofweek(now()) |
+———————+——————+
| 2017-04-19 20:25:41 | 4 |
+———————+——————+
1 row in set (0.00 sec)

mysql> SELECT now(),dayofmonth(now());
+———————+——————-+
| now() | dayofmonth(now()) |
+———————+——————-+
| 2017-04-19 20:25:51 | 19 |
+———————+——————-+
1 row in set (0.03 sec)

mysql> select now(),dayofyear(now());
+———————+——————+
| now() | dayofyear(now()) |
+———————+——————+
| 2017-04-19 20:26:00 | 109 |
+———————+——————+
1 row in set (0.00 sec)
复制代码
　　

　　dayname()

　　monthname()

Returns the week and month names of the date respectively

The name is Chinese or English controlled by the system variable lc_time_names (the default value is 'en_US')

mysql> set lc_time_names=’zh_CN’;
Query OK, 0 rows affected (0.00 sec)

Returns the day of the week, January, and year, respectively

Returns the week and month names of the date respectively

Guess you like