Mysql time Conversion Function usage page 1/2

Usage of mysql time Conversion Function

DAYOFWEEK (date)
Returns the index of the week of the date (1 = Sunday, 2 = Monday ,...... 7 = Saturday ). These index values correspond to the ODBC standard.
Mysql> select DAYOFWEEK (2007-10-31 );
-> 4

WEEKDAY (date)
Returns the week index of date (0 = Monday, 1 = Tuesday ,...... 6 = Sunday ).
Mysql> select WEEKDAY ('2017-10-31 13:05:00 ');
-> 2
Mysql> select WEEKDAY ('2017-10-31 ');
-> 2

DAYOFMONTH (date)
Returns the date of a month in the range of 1 to 31.
Mysql> select DAYOFMONTH ('2017-10-31 ');
-> 31

DAYOFYEAR (date)
Returns the number of days in a year from 1 to 366.
Mysql> select DAYOFYEAR ('2017-10-31 ');
-> 304


MONTH (date)
Returns the month of date, ranging from 1 to 12.
Mysql> select MONTH ('2017-10-31 ');
-> 10

DAYNAME (date)
Returns the week name of date.
Mysql> select DAYNAME ("2007-10-31 ");
-> 'Wednesday'

MONTHNAME (date)
Returns the month name of date.
Mysql> select MONTHNAME ("2007-10-31 ");
-> 'October'

QUARTER (date)
Returns the quarter of a year from date, ranging from 1 to 4.
Mysql> select QUARTER ('2017-10-31 ');
-> 4

WEEK (date)

WEEK (date, first)
If Sunday is the first day of a week, there is a single parameter that returns the number of weeks of the date, ranging from 0 to 52. Two Parameter formats: WEEK () allows you to specify whether the WEEK starts on Sunday or Monday. If the second parameter is 0, the week starts from Sunday, and if the second parameter is 1, it starts from Monday.
Mysql> select WEEK ('2017-02-20 ');
-> 7
Mysql> select WEEK ('2017-02-20 ', 0 );
-> 7
Mysql> select WEEK ('2017-02-20 ', 1 );
-> 8

YEAR (date)
Returns the year of date, ranging from 1000 to 9999.
Mysql> select YEAR ('98-02-03 ');
-> 1998

HOUR (time)
Returns the hour of time, ranging from 0 to 23.
Mysql> select HOUR ('10: 05: 03 ');
-> 10

MINUTE (time)
Returns the minute of time, ranging from 0 to 59.
Mysql> select MINUTE ('98-02-03 10:05:03 ');
-> 5

SECOND (time)
The number of seconds for the return time, ranging from 0 to 59.
Mysql> select SECOND ('10: 05: 03 ');
-> 3

PERIOD_ADD (P, N)
Add N months to phase P (in the format of YYMM or YYYYMM ). Return Value in the format of YYYYMM. Note that the phase parameter P is not a date value.
Mysql> select PERIOD_ADD (9801,2 );
-> 199803

PERIOD_DIFF (P1, P2)
Returns the number of months between period P1 and P2. P1 and P2 should be in the format of YYMM or YYYYMM. Note that the period parameters P1 and P2 are not date values.
Mysql> select PERIOD_DIFF (9802,199703 );
-> 11

DATE_ADD (date, INTERVAL expr type)

DATE_SUB (date, INTERVAL expr type)

ADDDATE (date, INTERVAL expr type)

SUBDATE (date, INTERVAL expr type)
These functions perform date operations. For MySQL 3.22, they are new. ADDDATE () and SUBDATE () are synonyms of DATE_ADD () and DATE_SUB.
In MySQL 3.23, you can use + and-instead of DATE_ADD () and DATE_SUB (). (See the example) date is a specified start date.
DATETIME or DATE value. expr is an expression that specifies the value to be added to the start DATE or the value to be subtracted from the start DATE. expr is a string.
A "-" indicates the negative interval. Type is a keyword that specifies how the expression should be interpreted. EXTRACT (type FROM date) function FROM date
Returns the "type" interval. The following table shows how the type and expr parameters are associated: The type value indicates the expected expr format.
SECOND SECONDS
MINUTE MINUTES
HOUR time HOURS
DAY DAYS
MONTH-MONTH MONTHS
YEAR YEARS
MINUTE_SECOND MINUTES and SECONDS "MINUTES: SECONDS"
HOUR_MINUTE hour and minute "HOURS: MINUTES"
DAY_HOUR and hour "days hours"
YEAR_MONTH and month "YEARS-MONTHS"
HOUR_SECOND hour, minute, "HOURS: MINUTES: SECONDS"
DAY_MINUTE day, hour, minute "days hours: MINUTES"
DAY_SECOND day, hour, minute, second "days hours: MINUTES: SECONDS"

MySQL allows any punctuation Separator in the expr format. It indicates that the recommended Delimiter is displayed. If the date parameter is a DATE value and your calculation only contains the YEAR, MONTH, and DAY sections (that is, there is no time section), the result is a DATE value. Otherwise, the result is a DATETIME value.

Mysql> SELECT "23:59:59" + INTERVAL 1 SECOND;
-> 00:00:00
Mysql> select interval 1 DAY + "1997-12-31 ";
-> 1998-01-01
Mysql> SELECT "1998-01-01"-INTERVAL 1 SECOND;
-> 1997-12-31 23:59:59
Mysql> SELECT DATE_ADD ("23:59:59 ",
INTERVAL 1 SECOND );
-> 00:00:00
Mysql> SELECT DATE_ADD ("23:59:59 ",
INTERVAL 1 DAY );
-> 23:59:59
Mysql> SELECT DATE_ADD ("23:59:59 ",
INTERVAL "1:1" MINUTE_SECOND );
-> 00:01:00
Mysql> SELECT DATE_SUB ("00:00:00 ",
INTERVAL "1" DAY_SECOND );
-> 1997-12-30 22:58:59
Mysql> SELECT DATE_ADD ("00:00:00 ",
INTERVAL "-1 10" DAY_HOUR );
-> 1997-12-30 14:00:00
Mysql> SELECT DATE_SUB ("1998-01-02", INTERVAL 31 DAY );
-> 1997-12-02
Mysql> select extract (year from "maid ");
-> 1999
Mysql> select extract (YEAR_MONTH FROM "01:02:03 ");
-> 199907
Mysql> select extract (DAY_MINUTE FROM "01:02:03 ");
-> 20102

If you specify an interval value that is too short (excluding the expected interval of the type keyword), MySQL assumes that you have saved the leftmost portion of the interval value. For example, if you specify a type of DAY_SECOND, the value of expr is expected to be one day, hour, minute, and second. If you specify a value like "", MySQL assumes that the days and hours are lost and the value represents minutes and seconds. In other words, "" DAY_SECOND is interpreted as it is equivalent to "" MINUTE_SECOND, this interpretation of MySQL's TIME value indicates that the elapsed TIME is not as a one-day TIME. If you use an incorrect date, the result is NULL. If you increase MONTH, YEAR_MONTH, or YEAR and the result date is greater than the maximum number of days of the new MONTH, the day is adjusted by the maximum number of days of the new moon.