Mysql：函数之三： date and time functions

11.6. Date and Time Functions

This section describes the functions that can be used to manipulate temporal values. See Section 10.3, “Date and Time Types”, for a description of the range of values each date and time type has and the valid formats in which values may be specified.

Name	Description
ADDDATE()(v4.1.1)	Add dates
ADDTIME()(v4.1.1)	Add time
CONVERT_TZ()(v4.1.3)	Convert from one timezone to another
CURDATE()	Return the current date
CURRENT_DATE(), CURRENT_DATE	Synonyms for CURDATE()
CURRENT_TIME(), CURRENT_TIME	Synonyms for CURTIME()
CURRENT_TIMESTAMP(), CURRENT_TIMESTAMP	Synonyms for NOW()
CURTIME()	Return the current time
DATE_ADD()	Add two dates
DATE_FORMAT()	Format date as specified
DATE_SUB()	Subtract two dates
DATE()(v4.1.1)	Extract the date part of a date or datetime expression
DATEDIFF()(v4.1.1)	Subtract two dates
DAY()(v4.1.1)	Synonym for DAYOFMONTH()
DAYNAME()(v4.1.21)	Return the name of the weekday
DAYOFMONTH()	Return the day of the month (0-31)
DAYOFWEEK()	Return the weekday index of the argument
DAYOFYEAR()	Return the day of the year (1-366)
EXTRACT	Extract part of a date
FROM_DAYS()	Convert a day number to a date
FROM_UNIXTIME()	Format UNIX timestamp as a date
GET_FORMAT()(v4.1.1)	Return a date format string
HOUR()	Extract the hour
LAST_DAY(v4.1.1)	Return the last day of the month for the argument
LOCALTIME(), LOCALTIME	Synonym for NOW()
LOCALTIMESTAMP, LOCALTIMESTAMP()(v4.0.6)	Synonym for NOW()
MAKEDATE()(v4.1.1)	Create a date from the year and day of year
MAKETIME(v4.1.1)	MAKETIME()
MICROSECOND()(v4.1.1)	Return the microseconds from argument
MINUTE()	Return the minute from the argument
MONTH()	Return the month from the date passed
MONTHNAME()(v4.1.21)	Return the name of the month
NOW()	Return the current date and time
PERIOD_ADD()	Add a period to a year-month
PERIOD_DIFF()	Return the number of months between periods
QUARTER()	Return the quarter from a date argument
SEC_TO_TIME()	Converts seconds to 'HH:MM:SS' format
SECOND()	Return the second (0-59)
STR_TO_DATE()(v4.1.1)	Convert a string to a date
SUBDATE()	A synonym for DATE_SUB() when invoked with three arguments
SUBTIME()(v4.1.1)	Subtract times
SYSDATE()	Return the time at which the function executes
TIME_FORMAT()	Format as time
TIME_TO_SEC()	Return the argument converted to seconds
TIME()(v4.1.1)	Extract the time portion of the expression passed
TIMEDIFF()(v4.1.1)	Subtract time
TIMESTAMP()(v4.1.1)	With a single argument, this function returns the date or datetime expression; with two arguments, the sum of the arguments
TIMESTAMPADD()(v5.0.0)	Add an interval to a datetime expression
TIMESTAMPDIFF()(v5.0.0)	Subtract an interval from a datetime expression
TO_DAYS()	Return the date argument converted to days
UNIX_TIMESTAMP()	Return a UNIX timestamp
UTC_DATE()(v4.1.1)	Return the current UTC date
UTC_TIME()(v4.1.1)	Return the current UTC time
UTC_TIMESTAMP()(v4.1.1)	Return the current UTC date and time
WEEK()	Return the week number
WEEKDAY()	Return the weekday index
WEEKOFYEAR()(v4.1.1)	Return the calendar week of the date (0-53)
YEAR()	Return the year
YEARWEEK()	Return the year and week

Here is an example that uses date functions. The following query selects all rows with a date_col value from within the last 30 days:

SELECT something FROM tbl_name
something
tbl_name
WHERE DATE_SUB(CURDATE(),INTERVAL 30 DAY) <= date_col;
date_col

The query also selects rows with dates that lie in the future.

Functions that expect date values usually accept datetime values and ignore the time part. Functions that expect time values usually accept datetime values and ignore the date part.

Functions that return the current date or time each are evaluated only once per query at the start of query execution. This means that multiple references to a function such as NOW() within a single query always produce the same result. (For our purposes, a single query also includes a call to a stored program (stored routine, trigger, or event) and all sub-programs called by that program.) This principle also applies to CURDATE(), CURTIME(), UTC_DATE(), UTC_TIME(), UTC_TIMESTAMP(), and to any of their synonyms.

The CURRENT_TIMESTAMP(), CURRENT_TIME(), CURRENT_DATE(), and FROM_UNIXTIME() functions return values in the connection's current time zone, which is available as the value of the time_zone system variable. In addition, UNIX_TIMESTAMP() assumes that its argument is a datetime value in the current time zone. See Section 9.7, “MySQL Server Time Zone Support”.

Some date functions can be used with “zero” dates or incomplete dates such as '2001-11-00', whereas others cannot. Functions that extract parts of dates typically work with incomplete dates and thus can return 0 when you might otherwise expect a non-zero value. For example:

mysql> SELECT DAYOFMONTH('2001-11-00'), MONTH('2005-00-00');
        -> 0, 0

Other functions expect complete dates and return NULL for incomplete dates. These include functions that perform date arithmetic or that map parts of dates to names. For example:

SELECT DATE_ADD('2006-05-00',INTERVAL 1 DAY);
SELECT DAYNAME('2006-05-00');

• ADDDATE(date,INTERVAL expr unit), ADDDATE(expr,days)

  When invoked with the INTERVAL form of the second argument, ADDDATE() is a synonym for DATE_ADD(). The related function SUBDATE() is a synonym for DATE_SUB(). For information on the INTERVAL unit argument, see the discussion for DATE_ADD().

  SELECT DATE_ADD('2008-01-02', INTERVAL 31 DAY);
  SELECT ADDDATE('2008-01-02', INTERVAL 31 DAY);

  When invoked with the days form of the second argument, MySQL treats it as an integer number of days to be added to expr.

  mysql> SELECT ADDDATE('2008-01-02', 31);
          -> '2008-02-02'
  

• ADDTIME(expr1,expr2)

  ADDTIME() adds expr2 to expr1 and returns the result. expr1 is a time or datetime expression, and expr2 is a time expression.

  SELECT ADDTIME('2007-12-31 23:59:59.999999', '1 1:1:1.000002');
  SELECT ADDTIME('01:00:00.999999', '02:00:00.999998');

• CONVERT_TZ(dt,from_tz,to_tz)

  CONVERT_TZ() converts a datetime value dt from the time zone given by from_tz to the time zone given by to_tz and returns the resulting value. Time zones are specified as described in Section 9.7, “MySQL Server Time Zone Support”. This function returns NULL if the arguments are invalid.

  If the value falls out of the supported range of the TIMESTAMP type when converted from from_tz to UTC, no conversion occurs. The TIMESTAMP range is described in Section 10.1.2, “Overview of Date and Time Types”.

  SELECT CONVERT_TZ('2004-01-01 12:00:00','GMT','MET');
  SELECT CONVERT_TZ('2004-01-01 12:00:00','+00:00','+10:00');

  Note

  To use named time zones such as 'MET' or 'Europe/Moscow', the time zone tables must be properly set up. See Section 9.7, “MySQL Server Time Zone Support”, for instructions.

  Before MySQL 5.1.17, if you intend to use CONVERT_TZ() while other tables are locked with LOCK TABLES, you must also lock the mysql.time_zone_name table. See Section 12.4.5, “LOCK TABLES and UNLOCK TABLES Syntax”.

• CURDATE()

  Returns the current date as a value in 'YYYY-MM-DD' or YYYYMMDD format, depending on whether the function is used in a string or numeric context.

  SELECT CURDATE();
  SELECT CURDATE() + 0;

• CURRENT_DATE, CURRENT_DATE()

  CURRENT_DATE and CURRENT_DATE() are synonyms for CURDATE().

• CURTIME()

  Returns the current time as a value in 'HH:MM:SS' or HHMMSS.uuuuuu format, depending on whether the function is used in a string or numeric context. The value is expressed in the current time zone.

  SELECT CURTIME();
  SELECT CURTIME() + 0;

• CURRENT_TIME, CURRENT_TIME()

  CURRENT_TIME and CURRENT_TIME() are synonyms for CURTIME().

• CURRENT_TIMESTAMP, CURRENT_TIMESTAMP()

  CURRENT_TIMESTAMP and CURRENT_TIMESTAMP() are synonyms for NOW().

• DATE(expr)

  Extracts the date part of the date or datetime expression expr.

  mysql> SELECT DATE('2003-12-31 01:02:03');
          -> '2003-12-31'
  

• DATEDIFF(expr1,expr2)

  DATEDIFF() returns expr1 – expr2 expressed as a value in days from one date to the other. expr1 and expr2 are date or date-and-time expressions. Only the date parts of the values are used in the calculation.

  SELECT DATEDIFF('2007-12-31 23:59:59','2007-12-30');
  SELECT DATEDIFF('2010-11-30 23:59:59','2010-12-31');

• DATE_ADD(date,INTERVAL expr unit), DATE_SUB(date,INTERVAL expr unit)

  These functions perform date arithmetic. The date argument specifies the starting date or datetime value. expr is an expression specifying the interval value to be added or subtracted from the starting date. expr is a string; it may start with a “-” for negative intervals. unit is a keyword indicating the units in which the expression should be interpreted.

  The INTERVAL keyword and the unit specifier are not case sensitive.

  The following table shows the expected form of the expr argument for each unit value.

  unit Value	Expected expr Format
  MICROSECOND	MICROSECONDS
  SECOND	SECONDS
  MINUTE	MINUTES
  HOUR	HOURS
  DAY	DAYS
  WEEK	WEEKS
  MONTH	MONTHS
  QUARTER	QUARTERS
  YEAR	YEARS
  SECOND_MICROSECOND	'SECONDS.MICROSECONDS'
  MINUTE_MICROSECOND	'MINUTES:SECONDS.MICROSECONDS'
  MINUTE_SECOND	'MINUTES:SECONDS'
  HOUR_MICROSECOND	'HOURS:MINUTES:SECONDS.MICROSECONDS'
  HOUR_SECOND	'HOURS:MINUTES:SECONDS'
  HOUR_MINUTE	'HOURS:MINUTES'
  DAY_MICROSECOND	'DAYS HOURS:MINUTES:SECONDS.MICROSECONDS'
  DAY_SECOND	'DAYS HOURS:MINUTES:SECONDS'
  DAY_MINUTE	'DAYS HOURS:MINUTES'
  DAY_HOUR	'DAYS HOURS'
  YEAR_MONTH	'YEARS-MONTHS'

  The return value depends on the arguments:

  • DATETIME if the first argument is a DATETIME (or TIMESTAMP) value, or if the first argument is a DATE and the unit value uses HOURS, MINUTES, or SECONDS.

  • String otherwise.

  To ensure that the result is DATETIME, you can use CAST() to convert the first argument to DATETIME.

  MySQL allows any punctuation delimiter in the expr format. Those shown in the table are the suggested delimiters. If the date argument is a DATE value and your calculations involve only YEAR, MONTH, and DAY parts (that is, no time parts), the result is a DATE value. Otherwise, the result is a DATETIME value.

  Date arithmetic also can be performed using INTERVAL together with the + or - operator:

  date
  expr
  unit
  date
  expr
  unit

  INTERVAL expr unit is allowed on either side of the + operator if the expression on the other side is a date or datetime value. For the - operator, INTERVAL expr unit is allowed only on the right side, because it makes no sense to subtract a date or datetime value from an interval.

  SELECT '2008-12-31 23:59:59' + INTERVAL 1 SECOND;
  SELECT INTERVAL 1 DAY + '2008-12-31';
  SELECT '2005-01-01' - INTERVAL 1 SECOND;
  SELECT DATE_ADD('2000-12-31 23:59:59',
                  INTERVAL 1 SECOND);
  SELECT DATE_ADD('2010-12-31 23:59:59',
                  INTERVAL 1 DAY);
  SELECT DATE_ADD('2100-12-31 23:59:59',
                  INTERVAL '1:1' MINUTE_SECOND);
  SELECT DATE_SUB('2005-01-01 00:00:00',
                  INTERVAL '1 1:1:1' DAY_SECOND);
  SELECT DATE_ADD('1900-01-01 00:00:00',
                  INTERVAL '-1 10' DAY_HOUR);
  SELECT DATE_SUB('1998-01-02', INTERVAL 31 DAY);
  SELECT DATE_ADD('1992-12-31 23:59:59.000002',
  INTERVAL '1.999999' SECOND_MICROSECOND);

  If you specify an interval value that is too short (does not include all the interval parts that would be expected from the unit keyword), MySQL assumes that you have left out the leftmost parts of the interval value. For example, if you specify a unit of DAY_SECOND, the value of expr is expected to have days, hours, minutes, and seconds parts. If you specify a value like '1:10', MySQL assumes that the days and hours parts are missing and the value represents minutes and seconds. In other words, '1:10' DAY_SECOND is interpreted in such a way that it is equivalent to '1:10' MINUTE_SECOND. This is analogous to the way that MySQL interprets TIME values as representing elapsed time rather than as a time of day.

  Because expr is treated as a string, be careful if you specify a non-string value with INTERVAL. For example, with an interval specifier of HOUR_MINUTE, 6/4 evaluates to 1.5000 and is treated as 1 hour, 5000 minutes:

  SELECT 6/4;
  SELECT DATE_ADD('2009-01-01', INTERVAL 6/4 HOUR_MINUTE);

  To ensure interpretation of the interval value as you expect, a CAST() operation may be used. To treat 6/4 as 1 hour, 5 minutes, cast it to a DECIMAL value with a single fractional digit:

  SELECT CAST(6/4 AS DECIMAL(3,1));
  SELECT DATE_ADD('1970-01-01 12:00:00',
                  INTERVAL CAST(6/4 AS DECIMAL(3,1)) HOUR_MINUTE);

  If you add to or subtract from a date value something that contains a time part, the result is automatically converted to a datetime value:

  SELECT DATE_ADD('2013-01-01', INTERVAL 1 DAY);
  SELECT DATE_ADD('2013-01-01', INTERVAL 1 HOUR);

  If you add MONTH, YEAR_MONTH, or YEAR and the resulting date has a day that is larger than the maximum day for the new month, the day is adjusted to the maximum days in the new month:

  mysql> SELECT DATE_ADD('2009-01-30', INTERVAL 1 MONTH);
          -> '2009-02-28'
  

  Date arithmetic operations require complete dates and do not work with incomplete dates such as '2006-07-00' or badly malformed dates:

  SELECT DATE_ADD('2006-07-00', INTERVAL 1 DAY);
  SELECT '2005-03-32' + INTERVAL 1 MONTH;

• DATE_FORMAT(date,format)

  Formats the date value according to the format string.

  The following specifiers may be used in the format string. The “%” character is required before format specifier characters.

  Specifier	Description
  %a	Abbreviated weekday name (Sun..Sat)
  %b	Abbreviated month name (Jan..Dec)
  %c	Month, numeric (0..12)
  %D	Day of the month with English suffix (0th, 1st, 2nd, 3rd, …)
  %d	Day of the month, numeric (00..31)
  %e	Day of the month, numeric (0..31)
  %f	Microseconds (000000..999999)
  %H	Hour (00..23)
  %h	Hour (01..12)
  %I	Hour (01..12)
  %i	Minutes, numeric (00..59)
  %j	Day of year (001..366)
  %k	Hour (0..23)
  %l	Hour (1..12)
  %M	Month name (January..December)
  %m	Month, numeric (00..12)
  %p	AM or PM
  %r	Time, 12-hour (hh:mm:ss followed by AM or PM)
  %S	Seconds (00..59)
  %s	Seconds (00..59)
  %T	Time, 24-hour (hh:mm:ss)
  %U	Week (00..53), where Sunday is the first day of the week
  %u	Week (00..53), where Monday is the first day of the week
  %V	Week (01..53), where Sunday is the first day of the week; used with %X
  %v	Week (01..53), where Monday is the first day of the week; used with %x
  %W	Weekday name (Sunday..Saturday)
  %w	Day of the week (0=Sunday..6=Saturday)
  %X	Year for the week where Sunday is the first day of the week, numeric, four digits; used with %V
  %x	Year for the week, where Monday is the first day of the week, numeric, four digits; used with %v
  %Y	Year, numeric, four digits
  %y	Year, numeric (two digits)
  %%	A literal “%” character
  %x	x, for any “x” not listed above

  Ranges for the month and day specifiers begin with zero due to the fact that MySQL allows the storing of incomplete dates such as '2014-00-00'.

  As of MySQL 5.1.12, the language used for day and month names and abbreviations is controlled by the value of the lc_time_names system variable (Section 9.8, “MySQL Server Locale Support”).

  As of MySQL 5.1.15, DATE_FORMAT() returns a string with a character set and collation given by character_set_connection and collation_connection so that it can return month and weekday names containing non-ASCII characters. Before 5.1.15, the return value is a binary string.

  SELECT DATE_FORMAT('2009-10-04 22:23:00', '%W %M %Y');
  SELECT DATE_FORMAT('2007-10-04 22:23:00', '%H:%i:%s');
  SELECT DATE_FORMAT('1900-10-04 22:23:00',
                  '%D %y %a %d %m %b %j');
  SELECT DATE_FORMAT('1997-10-04 22:23:00',
                  '%H %k %I %r %T %S %w');
  SELECT DATE_FORMAT('1999-01-01', '%X %V');
  SELECT DATE_FORMAT('2006-06-00', '%d');

• DATE_SUB(date,INTERVAL expr unit)

  See the description for DATE_ADD().

• DAY(date)

  DAY() is a synonym for DAYOFMONTH().

• DAYNAME(date)

  Returns the name of the weekday for date. As of MySQL 5.1.12, the language used for the name is controlled by the value of the lc_time_names system variable (Section 9.8, “MySQL Server Locale Support”).

  mysql> SELECT DAYNAME('2007-02-03');
          -> 'Saturday'
  

• DAYOFMONTH(date)

  Returns the day of the month for date, in the range 1 to 31, or 0 for dates such as '0000-00-00' or '2008-00-00' that have a zero day part.

  mysql> SELECT DAYOFMONTH('2007-02-03');
          -> 3
  

• DAYOFWEEK(date)

  Returns the weekday index for date (1 = Sunday, 2 = Monday, …, 7 = Saturday). These index values correspond to the ODBC standard.

  mysql> SELECT DAYOFWEEK('2007-02-03');
          -> 7
  

• DAYOFYEAR(date)

  Returns the day of the year for date, in the range 1 to 366.

  mysql> SELECT DAYOFYEAR('2007-02-03');
          -> 34
  

• EXTRACT(unit FROM date)

  The EXTRACT() function uses the same kinds of unit specifiers as DATE_ADD() or DATE_SUB(), but extracts parts from the date rather than performing date arithmetic.

  SELECT EXTRACT(YEAR FROM '2009-07-02');
  SELECT EXTRACT(YEAR_MONTH FROM '2009-07-02 01:02:03');
  SELECT EXTRACT(DAY_MINUTE FROM '2009-07-02 01:02:03');
  SELECT EXTRACT(MICROSECOND
  FROM '2003-01-02 10:30:00.000123');

• FROM_DAYS(N)

  Given a day number N, returns a DATE value.

  mysql> SELECT FROM_DAYS(730669);
          -> '2007-07-03'
  

  Use FROM_DAYS() with caution on old dates. It is not intended for use with values that precede the advent of the Gregorian calendar (1582). See Section 11.7, “What Calendar Is Used By MySQL?”.

• FROM_UNIXTIME(unix_timestamp), FROM_UNIXTIME(unix_timestamp,format)

  Returns a representation of the unix_timestamp argument as a value in 'YYYY-MM-DD HH:MM:SS' or YYYYMMDDHHMMSS.uuuuuu format, depending on whether the function is used in a string or numeric context. The value is expressed in the current time zone. unix_timestamp is an internal timestamp value such as is produced by the UNIX_TIMESTAMP() function.

  If format is given, the result is formatted according to the format string, which is used the same way as listed in the entry for the DATE_FORMAT() function.

  SELECT FROM_UNIXTIME(1196440219);
  SELECT FROM_UNIXTIME(1196440219) + 0;
  SELECT FROM_UNIXTIME(UNIX_TIMESTAMP(),
  '%Y %D %M %h:%i:%s %x');

  Note: If you use UNIX_TIMESTAMP() and FROM_UNIXTIME() to convert between TIMESTAMP values and Unix timestamp values, the conversion is lossy because the mapping is not one-to-one in both directions. For details, see the description of the UNIX_TIMESTAMP() function.

• GET_FORMAT({DATE|TIME|DATETIME}, {'EUR'|'USA'|'JIS'|'ISO'|'INTERNAL'})

  Returns a format string. This function is useful in combination with the DATE_FORMAT() and the STR_TO_DATE() functions.

  The possible values for the first and second arguments result in several possible format strings (for the specifiers used, see the table in the DATE_FORMAT() function description). ISO format refers to ISO 9075, not ISO 8601.

  Function Call	Result
  GET_FORMAT(DATE,'USA')	'%m.%d.%Y'
  GET_FORMAT(DATE,'JIS')	'%Y-%m-%d'
  GET_FORMAT(DATE,'ISO')	'%Y-%m-%d'
  GET_FORMAT(DATE,'EUR')	'%d.%m.%Y'
  GET_FORMAT(DATE,'INTERNAL')	'%Y%m%d'
  GET_FORMAT(DATETIME,'USA')	'%Y-%m-%d %H.%i.%s'
  GET_FORMAT(DATETIME,'JIS')	'%Y-%m-%d %H:%i:%s'
  GET_FORMAT(DATETIME,'ISO')	'%Y-%m-%d %H:%i:%s'
  GET_FORMAT(DATETIME,'EUR')	'%Y-%m-%d %H.%i.%s'
  GET_FORMAT(DATETIME,'INTERNAL')	'%Y%m%d%H%i%s'
  GET_FORMAT(TIME,'USA')	'%h:%i:%s %p'
  GET_FORMAT(TIME,'JIS')	'%H:%i:%s'
  GET_FORMAT(TIME,'ISO')	'%H:%i:%s'
  GET_FORMAT(TIME,'EUR')	'%H.%i.%s'
  GET_FORMAT(TIME,'INTERNAL')	'%H%i%s'

  TIMESTAMP can also be used as the first argument to GET_FORMAT(), in which case the function returns the same values as for DATETIME.

  SELECT DATE_FORMAT('2003-10-03',GET_FORMAT(DATE,'EUR'));
  SELECT STR_TO_DATE('10.31.2003',GET_FORMAT(DATE,'USA'));

• HOUR(time)

  Returns the hour for time. The range of the return value is 0 to 23 for time-of-day values. However, the range of TIME values actually is much larger, so HOUR can return values greater than 23.

  SELECT HOUR('10:05:03');
  SELECT HOUR('272:59:59');

• LAST_DAY(date)

  Takes a date or datetime value and returns the corresponding value for the last day of the month. Returns NULL if the argument is invalid.

  SELECT LAST_DAY('2003-02-05');
  SELECT LAST_DAY('2004-02-05');
  SELECT LAST_DAY('2004-01-01 01:01:01');
  SELECT LAST_DAY('2003-03-32');

• LOCALTIME, LOCALTIME()

  LOCALTIME and LOCALTIME() are synonyms for NOW().

• LOCALTIMESTAMP, LOCALTIMESTAMP()

  LOCALTIMESTAMP and LOCALTIMESTAMP() are synonyms for NOW().

• MAKEDATE(year,dayofyear)

  Returns a date, given year and day-of-year values. dayofyear must be greater than 0 or the result is NULL.

  SELECT MAKEDATE(2011,31), MAKEDATE(2011,32);
  SELECT MAKEDATE(2011,365), MAKEDATE(2014,365);
  SELECT MAKEDATE(2011,0);

• MAKETIME(hour,minute,second)

  Returns a time value calculated from the hour, minute, and second arguments.

  mysql> SELECT MAKETIME(12,15,30);
          -> '12:15:30'
  

• MICROSECOND(expr)

  Returns the microseconds from the time or datetime expression expr as a number in the range from 0 to 999999.

  SELECT MICROSECOND('12:00:00.123456');
  SELECT MICROSECOND('2009-12-31 23:59:59.000010');

• MINUTE(time)

  Returns the minute for time, in the range 0 to 59.

  mysql> SELECT MINUTE('2008-02-03 10:05:03');
          -> 5
  

• MONTH(date)

  Returns the month for date, in the range 1 to 12 for January to December, or 0 for dates such as '0000-00-00' or '2008-00-00' that have a zero month part.

  mysql> SELECT MONTH('2008-02-03');
          -> 2
  

• MONTHNAME(date)

  Returns the full name of the month for date. As of MySQL 5.1.12, the language used for the name is controlled by the value of the lc_time_names system variable (Section 9.8, “MySQL Server Locale Support”).

  mysql> SELECT MONTHNAME('2008-02-03');
          -> 'February'
  

• NOW()

  Returns the current date and time as a value in 'YYYY-MM-DD HH:MM:SS' or YYYYMMDDHHMMSS.uuuuuu format, depending on whether the function is used in a string or numeric context. The value is expressed in the current time zone.

  SELECT NOW();
  SELECT NOW() + 0;

  NOW() returns a constant time that indicates the time at which the statement began to execute. (Within a stored function or trigger, NOW() returns the time at which the function or triggering statement began to execute.) This differs from the behavior for SYSDATE(), which returns the exact time at which it executes.

  SELECT NOW(), SLEEP(2), NOW();
  SELECT SYSDATE(), SLEEP(2), SYSDATE();

  In addition, the SET TIMESTAMP statement affects the value returned by NOW() but not by SYSDATE(). This means that timestamp settings in the binary log have no effect on invocations of SYSDATE().

  See the description for SYSDATE() for additional information about the differences between the two functions.

• PERIOD_ADD(P,N)

  Adds N months to period P (in the format YYMM or YYYYMM). Returns a value in the format YYYYMM. Note that the period argument P is not a date value.

  mysql> SELECT PERIOD_ADD(200801,2);
          -> 200803
  

• PERIOD_DIFF(P1,P2)

  Returns the number of months between periods P1 and P2. P1 and P2 should be in the format YYMM or YYYYMM. Note that the period arguments P1 and P2 are not date values.

  mysql> SELECT PERIOD_DIFF(200802,200703);
          -> 11
  

• QUARTER(date)

  Returns the quarter of the year for date, in the range 1 to 4.

  mysql> SELECT QUARTER('2008-04-01');
          -> 2
  

• SECOND(time)

  Returns the second for time, in the range 0 to 59.

  mysql> SELECT SECOND('10:05:03');
          -> 3
  

• SEC_TO_TIME(seconds)

  Returns the seconds argument, converted to hours, minutes, and seconds, as a TIME value. The range of the result is constrained to that of the TIME data type. A warning occurs if the argument corresponds to a value outside that range.

  SELECT SEC_TO_TIME(2378);
  SELECT SEC_TO_TIME(2378) + 0;

• STR_TO_DATE(str,format)

  This is the inverse of the DATE_FORMAT() function. It takes a string str and a format string format. STR_TO_DATE() returns a DATETIME value if the format string contains both date and time parts, or a DATE or TIME value if the string contains only date or time parts. If the date, time, or datetime value extracted from str is illegal, STR_TO_DATE() returns NULL and produces a warning.

  The server scans str attempting to match format to it. The format string can contain literal characters and format specifiers beginning with %. Literal characters in format must match literally in str. Format specifiers in format must match a date or time part in str. For the specifiers that can be used in format, see the DATE_FORMAT() function description.

  SELECT STR_TO_DATE('01,5,2013','%d,%m,%Y');
  SELECT STR_TO_DATE('May 1, 2013','%M %d,%Y');

  Scanning starts at the beginning of str and fails if format is found not to match. Extra characters at the end of str are ignored.

  SELECT STR_TO_DATE('a09:30:17','a%h:%i:%s');
  SELECT STR_TO_DATE('a09:30:17','%h:%i:%s');
  SELECT STR_TO_DATE('09:30:17a','%h:%i:%s');

  Unspecified date or time parts have a value of 0, so incompletely specified values in str produce a result with some or all parts set to 0:

  SELECT STR_TO_DATE('abc','abc');
  SELECT STR_TO_DATE('9','%m');
  SELECT STR_TO_DATE('9','%s');

  Range checking on the parts of date values is as described in Section 10.3.1, “The DATETIME, DATE, and TIMESTAMP Types”. This means, for example, that “zero” dates or dates with part values of 0 are allowed unless the SQL mode is set to disallow such values.

  SELECT STR_TO_DATE('00/00/0000', '%m/%d/%Y');
  SELECT STR_TO_DATE('04/31/2004', '%m/%d/%Y');

  Note

  You cannot use format "%X%V" to convert a year-week string to a date because the combination of a year and week does not uniquely identify a year and month if the week crosses a month boundary. To convert a year-week to a date, then you should also specify the weekday:

  mysql> SELECT STR_TO_DATE('200442 Monday', '%X%V %W');
          -> '2004-10-18'
  

• SUBDATE(date,INTERVAL expr unit), SUBDATE(expr,days)

  When invoked with the INTERVAL form of the second argument, SUBDATE() is a synonym for DATE_SUB(). For information on the INTERVAL unit argument, see the discussion for DATE_ADD().

  SELECT DATE_SUB('2008-01-02', INTERVAL 31 DAY);
  SELECT SUBDATE('2008-01-02', INTERVAL 31 DAY);

  The second form allows the use of an integer value for days. In such cases, it is interpreted as the number of days to be subtracted from the date or datetime expression expr.

  mysql> SELECT SUBDATE('2008-01-02 12:00:00', 31);
          -> '2007-12-02 12:00:00'
  

• SUBTIME(expr1,expr2)

  SUBTIME() returns expr1 – expr2 expressed as a value in the same format as expr1. expr1 is a time or datetime expression, and expr2 is a time expression.

  SELECT SUBTIME('2007-12-31 23:59:59.999999','1 1:1:1.000002');
  SELECT SUBTIME('01:00:00.999999', '02:00:00.999998');

• SYSDATE()

  Returns the current date and time as a value in 'YYYY-MM-DD HH:MM:SS' or YYYYMMDDHHMMSS.uuuuuu format, depending on whether the function is used in a string or numeric context.

  SYSDATE() returns the time at which it executes. This differs from the behavior for NOW(), which returns a constant time that indicates the time at which the statement began to execute. (Within a stored function or trigger, NOW() returns the time at which the function or triggering statement began to execute.)

  SELECT NOW(), SLEEP(2), NOW();
  SELECT SYSDATE(), SLEEP(2), SYSDATE();

  In addition, the SET TIMESTAMP statement affects the value returned by NOW() but not by SYSDATE(). This means that timestamp settings in the binary log have no effect on invocations of SYSDATE().

  Because SYSDATE() can return different values even within the same statement, and is not affected by SET TIMESTAMP, it is non-deterministic and therefore unsafe for replication if statement-based binary logging is used. If that is a problem, you can use row-based logging, or start the server with the --sysdate-is-now option to cause SYSDATE() to be an alias for NOW(). The non-deterministic nature of SYSDATE() also means that indexes cannot be used for evaluating expressions that refer to it.

• TIME(expr)

  Extracts the time part of the time or datetime expression expr and returns it as a string.

  SELECT TIME('2003-12-31 01:02:03');
  SELECT TIME('2003-12-31 01:02:03.000123');

• TIMEDIFF(expr1,expr2)

  TIMEDIFF() returns expr1 – expr2 expressed as a time value. expr1 and expr2 are time or date-and-time expressions, but both must be of the same type.

  SELECT TIMEDIFF('2000:01:01 00:00:00',
  '2000:01:01 00:00:00.000001');
  SELECT TIMEDIFF('2008-12-31 23:59:59.000001',
                  '2008-12-30 01:01:01.000002');

• TIMESTAMP(expr), TIMESTAMP(expr1,expr2)

  With a single argument, this function returns the date or datetime expression expr as a datetime value. With two arguments, it adds the time expression expr2 to the date or datetime expression expr1 and returns the result as a datetime value.

  SELECT TIMESTAMP('2003-12-31');
  SELECT TIMESTAMP('2003-12-31 12:00:00','12:00:00');

• TIMESTAMPADD(unit,interval,datetime_expr)

  Adds the integer expression interval to the date or datetime expression datetime_expr. The unit for interval is given by the unit argument, which should be one of the following values: FRAC_SECOND (microseconds), SECOND, MINUTE, HOUR, DAY, WEEK, MONTH, QUARTER, or YEAR.

  Beginning with MySQL 5.1.24, it is possible to use MICROSECOND in place of FRAC_SECOND with this function, and FRAC_SECOND is deprecated.

  The unit value may be specified using one of keywords as shown, or with a prefix of SQL_TSI_. For example, DAY and SQL_TSI_DAY both are legal.

  SELECT TIMESTAMPADD(MINUTE,1,'2003-01-02');
  SELECT TIMESTAMPADD(WEEK,1,'2003-01-02');

• TIMESTAMPDIFF(unit,datetime_expr1,datetime_expr2)

  Returns datetime_expr2 – datetime_expr1, where datetime_expr1 and datetime_expr2 are date or datetime expressions. One expression may be a date and the other a datetime; a date value is treated as a datetime having the time part '00:00:00' where necessary. The unit for the result (an integer) is given by the unit argument. The legal values for unit are the same as those listed in the description of the TIMESTAMPADD() function.

  SELECT TIMESTAMPDIFF(MONTH,'2003-02-01','2003-05-01');
  SELECT TIMESTAMPDIFF(YEAR,'2002-05-01','2001-01-01');
  SELECT TIMESTAMPDIFF(MINUTE,'2003-02-01','2003-05-01 12:05:55');

  Note

  The order of the date or datetime arguments for this function is the opposite of that used with the TIMESTAMP() function when invoked with 2 arguments.

• TIME_FORMAT(time,format)

  This is used like the DATE_FORMAT() function, but the format string may contain format specifiers only for hours, minutes, seconds, and microseconds. Other specifiers produce a NULL value or 0.

  If the time value contains an hour part that is greater than 23, the %H and %k hour format specifiers produce a value larger than the usual range of 0..23. The other hour format specifiers produce the hour value modulo 12.

  mysql> SELECT TIME_FORMAT('100:00:00', '%H %k %h %I %l');
          -> '100 100 04 04 4'
  

• TIME_TO_SEC(time)

  Returns the time argument, converted to seconds.

  SELECT TIME_TO_SEC('22:23:00');
  SELECT TIME_TO_SEC('00:39:38');

• TO_DAYS(date)

  Given a date date, returns a day number (the number of days since year 0).

  SELECT TO_DAYS(950501);
  SELECT TO_DAYS('2007-10-07');

  TO_DAYS() is not intended for use with values that precede the advent of the Gregorian calendar (1582), because it does not take into account the days that were lost when the calendar was changed. For dates before 1582 (and possibly a later year in other locales), results from this function are not reliable. See Section 11.7, “What Calendar Is Used By MySQL?”, for details.

  Remember that MySQL converts two-digit year values in dates to four-digit form using the rules in Section 10.3, “Date and Time Types”. For example, '2008-10-07' and '08-10-07' are seen as identical dates:

  mysql> SELECT TO_DAYS('2008-10-07'), TO_DAYS('08-10-07');
          -> 733687, 733687
  

• UNIX_TIMESTAMP(), UNIX_TIMESTAMP(date)

  If called with no argument, returns a Unix timestamp (seconds since '1970-01-01 00:00:00' UTC) as an unsigned integer. If UNIX_TIMESTAMP() is called with a date argument, it returns the value of the argument as seconds since '1970-01-01 00:00:00' UTC. date may be a DATE string, a DATETIME string, a TIMESTAMP, or a number in the format YYMMDD or YYYYMMDD. The server interprets date as a value in the current time zone and converts it to an internal value in UTC. Clients can set their time zone as described in Section 9.7, “MySQL Server Time Zone Support”.

  SELECT UNIX_TIMESTAMP();
  SELECT UNIX_TIMESTAMP('2007-11-30 10:30:19');

  When UNIX_TIMESTAMP() is used on a TIMESTAMP column, the function returns the internal timestamp value directly, with no implicit “string-to-Unix-timestamp” conversion. If you pass an out-of-range date to UNIX_TIMESTAMP(), it returns 0.

  Note: If you use UNIX_TIMESTAMP() and FROM_UNIXTIME() to convert between TIMESTAMP values and Unix timestamp values, the conversion is lossy because the mapping is not one-to-one in both directions. For example, due to conventions for local time zone changes, it is possible for two UNIX_TIMESTAMP() to map two TIMESTAMP values to the same Unix timestamp value. FROM_UNIXTIME() will map that value back to only one of the original TIMESTAMP values. Here is an example, using TIMESTAMP values in the CET time zone:

  SELECT UNIX_TIMESTAMP('2005-03-27 03:00:00');
  SELECT UNIX_TIMESTAMP('2005-03-27 02:00:00');
  SELECT FROM_UNIXTIME(1111885200);

  If you want to subtract UNIX_TIMESTAMP() columns, you might want to cast the result to signed integers. See Section 11.9, “Cast Functions and Operators”.

• UTC_DATE, UTC_DATE()

  Returns the current UTC date as a value in 'YYYY-MM-DD' or YYYYMMDD format, depending on whether the function is used in a string or numeric context.

  mysql> SELECT UTC_DATE(), UTC_DATE() + 0;
          -> '2003-08-14', 20030814
  

• UTC_TIME, UTC_TIME()

  Returns the current UTC time as a value in 'HH:MM:SS' or HHMMSS.uuuuuu format, depending on whether the function is used in a string or numeric context.

  mysql> SELECT UTC_TIME(), UTC_TIME() + 0;
          -> '18:07:53', 180753.000000
  

• UTC_TIMESTAMP, UTC_TIMESTAMP()

  Returns the current UTC date and time as a value in 'YYYY-MM-DD HH:MM:SS' or YYYYMMDDHHMMSS.uuuuuu format, depending on whether the function is used in a string or numeric context.

  mysql> SELECT UTC_TIMESTAMP(), UTC_TIMESTAMP() + 0;
          -> '2003-08-14 18:08:04', 20030814180804.000000
  

• WEEK(date[,mode])

  This function returns the week number for date. The two-argument form of WEEK() allows you to specify whether the week starts on Sunday or Monday and whether the return value should be in the range from 0 to 53 or from 1 to 53. If the mode argument is omitted, the value of the default_week_format system variable is used. See Section 5.1.3, “Server System Variables”.

  The following table describes how the mode argument works.

  Mode	First day of week	Range	Week 1 is the first week …
  0	Sunday	0-53	with a Sunday in this year
  1	Monday	0-53	with more than 3 days this year
  2	Sunday	1-53	with a Sunday in this year
  3	Monday	1-53	with more than 3 days this year
  4	Sunday	0-53	with more than 3 days this year
  5	Monday	0-53	with a Monday in this year
  6	Sunday	1-53	with more than 3 days this year
  7	Monday	1-53	with a Monday in this year

  SELECT WEEK('2008-02-20');
  SELECT WEEK('2008-02-20',0);
  SELECT WEEK('2008-02-20',1);
  SELECT WEEK('2008-12-31',1);

  Note that if a date falls in the last week of the previous year, MySQL returns 0 if you do not use 2, 3, 6, or 7 as the optional mode argument:

  mysql> SELECT YEAR('2000-01-01'), WEEK('2000-01-01',0);
          -> 2000, 0
  

  One might argue that MySQL should return 52 for the WEEK() function, because the given date actually occurs in the 52nd week of 1999. We decided to return 0 instead because we want the function to return “the week number in the given year.” This makes use of the WEEK() function reliable when combined with other functions that extract a date part from a date.

  If you would prefer the result to be evaluated with respect to the year that contains the first day of the week for the given date, use 0, 2, 5, or 7 as the optional mode argument.

  mysql> SELECT WEEK('2000-01-01',2);
          -> 52
  

  Alternatively, use the YEARWEEK() function:

  SELECT YEARWEEK('2000-01-01');
  SELECT MID(YEARWEEK('2000-01-01'),5,2);

• WEEKDAY(date)

  Returns the weekday index for date (0 = Monday, 1 = Tuesday, … 6 = Sunday).

  SELECT WEEKDAY('2008-02-03 22:23:00');
  SELECT WEEKDAY('2007-11-06');

• WEEKOFYEAR(date)

  Returns the calendar week of the date as a number in the range from 1 to 53. WEEKOFYEAR() is a compatibility function that is equivalent to WEEK(date,3).

  mysql> SELECT WEEKOFYEAR('2008-02-20');
          -> 8
  

• YEAR(date)

  Returns the year for date, in the range 1000 to 9999, or 0 for the “zero” date.

  mysql> SELECT YEAR('1987-01-01');
          -> 1987
  

• YEARWEEK(date), YEARWEEK(date,mode)

  Returns year and week for a date. The mode argument works exactly like the mode argument to WEEK(). The year in the result may be different from the year in the date argument for the first and the last week of the year.

  mysql> SELECT YEARWEEK('1987-01-01');
          -> 198653
  

  Note that the week number is different from what the WEEK() function would return (0) for optional arguments 0 or 1, as WEEK() then returns the week in the context of the given year.