MySQL returns the current date and time (and converts the time) _ MySQL

MySQL obtains the bitsCN of the current date and time (and converts the time. com1.1 obtain the current date + time (date + time) function: in addition to the now () function to obtain the current date and time, MySQL also has the following function: current_timestamp () current_timestamplocaltime () localtimelocaltimestamp () localtimestamp these date and time functions are equivalent to now (). Considering that the now () function is short and easy to remember, we recommend that you always use now () to replace the functions listed above. 1.2 obtain the current date + time (date + time) function: the sysdate () date and time function is similar to the now () function. The difference is that: now () the execution start value is obtained, and sysdate () dynamically obtains the value during function execution. 2. obtain the current date function: curdate (). the following two date functions are equivalent to curdate (): current_date (), current_date 3. obtain the current time function: curtime (). the following two time functions are equivalent to curtime (): current_time (), current_time 4. obtain the current UTC date and time function: utc_date (), utc_time (), utc_timestamp () because our country is located in the East eight time zone, so the local time = UTC time + 8 hours. UTC time is very useful when your business involves multiple countries and regions. II. MySQL date and time Extract (select) function. 1. select each part of the date and time: date, time, year, quarter, month, day, hour, minute, second, microsecond set @ dt = '2017-09-10 07:15:30. 123456 '; select date (@ dt); -- 2008-09-10select 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 2. mySQL Extract () function, which can be implemented above Similar function: set @ dt = '2017-09-10 07:15:30. 123456 '; select extract (year from @ dt); -- 2008 select extract (quarter from @ dt); -- 3 select extract (month from @ dt ); -- 9 select extract (week from @ dt); -- 36 select extract (day from @ dt); -- 10 select extract (hour from @ dt ); -- 7 select extract (minute from @ dt); -- 15 select extract (second from @ dt); -- 30 select extract (microsecond from @ dt); -- 123456 select extract (Year_month from @ dt); -- 200809 select extract (day_hour from @ dt); -- 1007 select extract (day_minute from @ dt); -- 100715 select extract (day_second from @ dt ); -- 10071530 select extract (day_microsecond from @ dt); -- 10071530123456 select extract (hour_minute from @ dt); -- 715 select extract (hour_second from @ dt ); -- 71530 select extract (hour_microsecond from @ dt); -- 71530123456 select extract (minute_seco Nd from @ dt); -- 1530 select extract (minute_microsecond from @ dt); -- 1530123456 select extract (second_microsecond from @ dt); -- 30123456 MySQL Extract () except date () and time () functions, other functions must be complete. You can also select 'Day _ microsecond. Note that we will not only select day and microsecond, but choose from day of the date to microsecond. The only bad thing about the MySQL Extract () function is that you need to press the keyboard several more times. 3. MySQL dayof... Functions: dayofweek (), dayofmonth (), and dayofyear () return the date parameters in the positions of one week, one month, and one year. Set @ dt = '2014-08-08 '; select dayofweek (@ dt); -- 6 select dayofmonth (@ dt); -- 8 select dayofyear (@ dt ); -- the 221 date '2017-08-08 'is the first day of the week (1 = Sunday, 2 = Monday ,..., 7 = Saturday); January days in 8th; 221st days in a year. 4. MySQL week... Function: week (), weekofyear (), dayofweek (), weekday (), yearweek () set @ dt = '2017-08-08 '; select week (@ dt ); -- 31 select week (@ dt, 3); -- 32 select weekofyear (@ dt); -- 32 select dayofweek (@ dt); -- 6 select weekday (@ dt ); -- 4 select yearweek (@ dt); -- 200831 MySQL week () function, which can have two parameters. for details, see the manual. Similar to weekofyear () and week (), weekofyear is the day of the year in which the calculation "one day" is located. Weekofyear (@ dt) is equivalent to week (@ dt, 3 ). The MySQL weekday () function is similar to dayofweek () and returns the position of "one day" in a week. The difference lies in the reference standard, weekday :( 0 = Monday, 1 = Tuesday ,..., 6 = Sunday); dayofweek :( 1 = Sunday, 2 = Monday ,..., 7 = Saturday) MySQL yearweek () function, returns year (2008) + week position (31 ). 5. mySQL returns the week and month name functions: dayname (), monthname () set @ dt = '2017-08-08 '; select dayname (@ dt); -- Fridayselect monthname (@ dt ); -- August 6. mySQL last_day () function: returns the last day of the month. Select last_day ('2017-02-01 '); -- 2008-02-29select last_day ('2017-08-08'); -- 2008-08-31 3. MySQL date and time calculation function 1. mySQL adds a time interval for the date: 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 quarter, interval 1 year); select date_add (@ dt, interval-1 day); -- sub 1 day MySQL adddate (), addtime () function, which can be replaced by date_add. The following is an example of addtime () implemented by date_add (): mysql> set @ dt = '2017-08-09 12:12:33 '; mysql> select date_add (@ dt, interval '01: 15: 30 'hour_second); + ---------------------------------------------- + | date_add (@ dt, interval '01: 15: 30' hour_second) | + expiration + | 13:28:03 | + ------------------------------------------------------ + mysql> select date_add (@ dt, interval '1: 30 'day_second); + hour + | date_add (@ dt, interval '1 01:15:30 'day_second) | + hour + | 13:28:03 | + hour + date_add () function, added "1 hour 15 minutes 30 seconds" and "1 day 1 hour 15 minutes 30 seconds" for @ dt respectively ". Suggestion: Always use the date_add () date and time function to replace adddate () and addtime ().

2. MySQL is the date minus a time interval: the date_sub () MySQL date_sub () date and time functions are used in the same way as date_add. In addition, there are two subdate () and subtime () functions in MySQL. we recommend that you use date_sub () instead. 3. mySQL alternative date functions: period_add (P, N), period_diff (P1, P2) function parameter "P" format is "YYYYMM" or "YYMM ", the second parameter "N" indicates adding or subtracting N month ). MySQL period_add (P, N): date plus/minus N months. 4. MySQL date and time subtraction functions: datediff (date1, date2), timediff (time1, time2) MySQL datediff (date1, date2): two dates subtract date1-date2 and return days. Select datediff ('2017-08-08 ', '2017-08-01'); -- 7 select datediff ('2017-08-01 ', '2017-08-08 '); ---7 MySQL timediff (time1, time2): two dates minus time1-time2, return the time difference. Select timediff ('2017-08-08 08:08:08 ', '2017-08-08 00:00:00'); -- 08: 08: 08 select timediff ('08: 08: 08 ', '00: 00: 00'); -- 08:08:08 note: the two parameter types of the timediff (time1, time2) function must be the same. IV. MySQL date conversion function and time conversion function 1. mySQL (time, second) conversion function: time_to_sec (time), sec_to_time (seconds) select time_to_sec ('01: 00: 05 '); -- 3605 select sec_to_time (3605 ); -- '01: 00: 05 '2. mySQL (date, number of days) conversion function: to_days (date), from_days (days) select to_days ('2017-00-00 '); -- 0 select to_days ('2017-08-08 '); -- 733627 select from_days (0); -- '2017-00-00 'select from_days (0000); -- '2017-08-08' 3. mySQL Str to Date (string converted to Date) function: str_t O_date (str, format) select str_to_date ('2014/1/20180101', '% m/% d/% Y'); -- 2008-08-09select str_to_date ('2014/1/08 ', '% m/% d/% Y'); -- 2008-08-09select str_to_date ('08. 09.2008 ',' % m. % d. % Y'); -- 2008-08-09select 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'); -- 08:09:30 we can see that the str_to_date (str, format) conversion function can convert some disordered strings into date formats. In addition, it can be converted to time. For "format", see the MySQL manual. 4. mySQL Date/Time to Str (convert date/time to string) function: date_format (date, format), time_format (Time, format) MySQL Date, time conversion function: date_format (date, format), time_format (time, format) can convert a date/time to a variety of string formats. It is an inverse conversion of the str_to_date (str, format) function. 5. mySQL returns the time format function of a country or region: get_format () MySQL get_format () syntax: get_format (date | time | datetime, 'eur' | 'USA '| 'jis' | 'ISO '| all examples of 'internal' MySQL get_format () usage: select get_format (date, 'USA '); -- '% m. % d. % Y' select get_format (date, 'jis '); --' % Y-% m-% d' select get_format (date, 'ISO '); -- '% Y-% m-% d' select get_format (date, 'eur'); --' % d. % m. % Y' select get_format (date, 'internal'); -- '% Y % m % d' select get_format (dateti Me, 'USA'); -- '% Y-% m-% d % H. % I. % s' select get_format (datetime, 'jis '); --' % Y-% m-% d % H: % I: % s' select get_format (datetime, 'ISO '); --' % Y-% m-% d % H: % I: % s' select get_format (datetime, 'eur '); -- '% Y-% m-% d % H. % I. % s' select get_format (datetime, 'internal'); -- '% Y % m % d % H % I % s' select get_format (time, 'USA '); -- '% h: % I: % s % p' select get_format (time, 'jis'); -- '% H: % I: % s' select get_format (time, 'ISO '); --' % H: % I: % S 'Select get_format (time, 'eur'); -- '% H. % I. % s' select get_format (time, 'internal'); -- the '% H % I % s' MySQL get_format () function has fewer opportunities in actual use. 6. mySQL patchwork date and time functions: makdedate (year, dayofyear), maketime (hour, minute, second) select makedate (2001); -- '2017-01-31 'select makedate (, 32 ); -- '2014-02-01 'select maketime (2001, 30); -- '12: 15: 30' v. MySQL Timestamp function 1. mySQL obtains the current timestamp function: current_timestamp, current_timestamp () 2. mySQL (Unix timestamp, date) conversion functions: unix_timestamp (), unix_timestamp (date), from_unixtime (unix_timestamp), from_unixtime (unix_timestam P, format) 3. mySQL timestamp conversion, addition, and subtraction functions: timestamp (date) -- date to timestamptimestamp (dt, time) -- dt + timetimestampadd (unit, interval, datetime_expr) -- timestampdiff (unit, datetime_expr1, datetime_expr2) -- MySQL timestampdiff () function is more powerful than datediff () function, datediff () can only calculate the number of days between two dates. VI. MySQL timezone conversion function convert_tz (dt, from_tz, to_tz) select convert_tz ('2017-08-08 12:00:00 ',' + ',' + '); -- 04:00:00 time zone conversion can also be achieved through date_add, date_sub, timestampadd. Select date_add ('2017-08-08 12:00:00 ', interval-8 hour); -- 2008-08-08 04: 00: 00 select date_sub ('2017-08-08 12:00:00 ', interval 8 hour); -- 2008-08-08 04: 00: 00 select timestampadd (hour,-8, '2017-08-08 12:00:00 '); -- 2008-08-08 04: 00: 00bitsCN.com