sqlite

Khóa học miễn phí SQLite – Date & Time nhận dự án làm có lương

Posted on by user

SQLite – Date & Time

SQLite supports five date and time functions as follows −

Sr.No. Function Example
1 date(timestring, modifiers…) This returns the date in this format: YYYY-MM-DD
2 time(timestring, modifiers…) This returns the time as HH:MM:SS
3 datetime(timestring, modifiers…) This returns YYYY-MM-DD HH:MM:SS
4 julianday(timestring, modifiers…) This returns the number of days since noon in Greenwich on November 24, 4714 B.C.
5 strftime(timestring, modifiers…) This returns the date formatted according to the format string specified as the first argument formatted as per formatters explained below.

All the above five date and time functions take a time string as an argument. The time string is followed by zero or more modifiers. The strftime() function also takes a format string as its first argument. Following section will give you detail on different types of time strings and modifiers.

Time Strings

A time string can be in any of the following formats −

Sr.No. Time String Example
1 YYYY-MM-DD 2010-12-30
2 YYYY-MM-DD HH:MM 2010-12-30 12:10
3 YYYY-MM-DD HH:MM:SS.SSS 2010-12-30 12:10:04.100
4 MM-DD-YYYY HH:MM 30-12-2010 12:10
5 HH:MM 12:10
6 YYYY-MM-DDTHH:MM 2010-12-30 12:10
7 HH:MM:SS 12:10:01
8 YYYYMMDD HHMMSS 20101230 121001
9 now 2013-05-07

You can use the “T” as a literal character separating the date and the time.

Modifiers

The time string can be followed by zero or more modifiers that will alter date and/or time returned by any of the above five functions. Modifiers are applied from the left to right.

Following modifers are available in SQLite −

  • NNN days
  • NNN hours
  • NNN minutes
  • NNN.NNNN seconds
  • NNN months
  • NNN years
  • start of month
  • start of year
  • start of day
  • weekday N
  • unixepoch
  • localtime
  • utc

Formatters

SQLite provides a very handy function strftime() to format any date and time. You can use the following substitutions to format your date and time.

Substitution Description
%d Day of month, 01-31 %f Fractional seconds, SS.SSS %H Hour, 00-23 %j Day of year, 001-366 %J Julian day number, DDDD.DDDD %m Month, 00-12 %M Minute, 00-59 %s Seconds since 1970-01-01 %S Seconds, 00-59 %w Day of week, 0-6 (0 is Sunday) %W Week of year, 01-53 %Y Year, YYYY %% % symbol

Examples

Let”s try various examples now using SQLite prompt. Following command computes the current date.

sqlite> SELECT date(''now'');
2013-05-07

Following command computes the last day of the current month.

sqlite> SELECT date(''now'',''start of month'',''+1 month'',''-1 day'');
2013-05-31

Following command computes the date and time for a given UNIX timestamp 1092941466.

sqlite> SELECT datetime(1092941466, ''unixepoch'');
2004-08-19 18:51:06

Following command computes the date and time for a given UNIX timestamp 1092941466 and compensate for your local timezone.

sqlite> SELECT datetime(1092941466, ''unixepoch'', ''localtime'');
2004-08-19 13:51:06

Following command computes the current UNIX timestamp.

sqlite> SELECT strftime(''%s'',''now'');
1393348134

Following command computes the number of days since the signing of the US Declaration of Independence.

sqlite> SELECT julianday(''now'') - julianday(''1776-07-04'');
86798.7094695023

Following command computes the number of seconds since a particular moment in 2004.

sqlite> SELECT strftime(''%s'',''now'') - strftime(''%s'',''2004-01-01 02:34:56'');
295001572

Following command computes the date of the first Tuesday in October for the current year.

sqlite> SELECT date(''now'',''start of year'',''+9 months'',''weekday 2'');
2013-10-01

Following command computes the time since the UNIX epoch in seconds (like strftime(”%s”,”now”) except includes fractional part).

sqlite> SELECT (julianday(''now'') - 2440587.5)*86400.0;
1367926077.12598

To convert between UTC and local time values when formatting a date, use the utc or localtime modifiers as follows −

sqlite> SELECT time(''12:00'', ''localtime'');
05:00:00

sqlite> SELECT time(''12:00'', ''utc'');
19:00:00

Khóa học lập trình tại Toidayhoc vừa học vừa làm dự án vừa nhận lương: Khóa học lập trình nhận lương tại trung tâm Toidayhoc

user