SQL Server Date and time functions

1, the common date method (below getdate () = ' 2006-11-08 13:37:56.233 ')

(1) Datename (DatePart, date)

Returns a String that represents the specified date portion of the specified date. DatePart See the list below.

Select Datename (DayGetdate-- return 8

(2) DATEPART (DatePart, date)

Returns an integer that represents the specified date portion of the specified date.

Select Datepart (yearGetdate-- return to 2006

(3) DATEADD (DatePart, number, date)

Returns a new datetime value that is added to the specified date after a time interval.

Select Dateadd 1 Getdate -- date plus one week after the current date

(4) DATEDIFF (DatePart, StartDate, EndDate)

Returns the number of date boundaries and time boundaries across two specified dates.

Select Datediff (Month'2006-10-11'2006-11-01')  -- returns 1

(5) Day (date)

Returns an integer that represents the day datepart portion of the specified date.

Select  Day (Getdate-- Date: 2014-11-08 08:56:45.903, return 8

(6) GETDATE ()

Returns the current system date and time as a datetime value in the SQL Server 2005 standard internal format.

Select Getdate -- back to 2006-11-08 13:37:56.2

(7) MONTH (date)

Returns an integer that represents the month portion of a specified date.

Select Month (Getdate-- return

(8) Year (date)

Returns an integer that represents the year part of the specified date.

Select  Year (Getdate-- return to 2006

2. Take a specific date

(1) The day of the week to get the current date

Select Datename Getdate -- Wednesday

(2) Calculate which day is the Monday of this week

Select Dateadd(Week,Datediff(Week,'1900-01-01',Getdate()),'1900-01-01' )  --back to 2006-11-06 00:00:00.000--orSelect Dateadd(Week,Datediff(Week,0,Getdate()),0)

(3) The first day of the current quarter

Select Dateadd Datediff 0 Getdate 0)  -- back to 2006-10-01 00:00:00.0

(4) How to get the number of days in a month

Select  Day Dateadd - 3 Dateadd Datediff 0 ' 2006-02-03 ' + 1 0 -- back to

(5) How many days of a quarter

Declare @m Tinyint,@time smalldatetimeSelect @m = Month(Getdate()) Select @m =  Case                   when @m between 1  and 3  Then 1                  when @m between 4  and 6  Then 4                  when @m between 7  and 9  Then 7                 Else Ten            EndSelect @time = Datename( Year,Getdate())+ '-' + Convert(Varchar(Ten),@m)+ '-01' Select Datediff( Day,@time,Dateadd(MM,3,@time))--back to

(6) Date of acquisition (YYYY-MM-DD)

Select Convert (Varchar(Getdate )- return to 2006-11-

3. Other

(1)--The following example specifies a date as a number. The database engine interprets 0 as January 1, 1900.

Select Month (0Day (0year (0)

-- The following two sentences are equivalent Select Datename 0 )Selectdatename'1900-01-01')

(2) SET Datefirst {number | @number_var}

Set the first day of the week to a number from 1 to 7.

Set 1 -- indicates that the first day of the week is "Monday" Select Datename Getdate ())  --WednesdaySelectDatepartGetdate--  Returns 3Select@ @DATEFIRST  -- view current settings

(3) SET DateFormat {format | @format_var}

Sets the order of the date parts (month/day/year) that are used to enter datetime or smalldatetime data.
... Valid parameters include MDY, dmy, Ymd, YDM, MyD, and Dym.
... This setting is used only in the interpretation when converting a string to a date value. It does not affect the display of date values.
... Set DateFormat settings are set at execution or runtime, not at parse time.
... Set DateFormat overrides the implicit date format setting for set LANGUAGE.
Here is an example:

--Set Date format to year, day, month.SetDateFormat YDM;GoDeclare @datevar Datetime;Set @datevar = '1998/31/12';Select @datevar  asDatevar;Go--Set Date format to year, month, day.SetDateFormat Ymd;GoDeclare @datevar Datetime;Set @datevar = '1998/12/31';Select @datevar  asDatevar;Go

(4) List of date parts

Date part	Abbreviation
Year	YY, yyyy
Quarter	QQ, Q
Month	MM, M
DayOfYear	Dy, y
Day	DD, D
Week	WK, WW
Weekday	Dw
Hour	hh
Minute	MI, n
Second	SS, S
Millisecond	Ms

Data type	Range	Accuracy
Datetime	January 1, 1753 to December 31, 9999	3.33 ms
smalldatetime	January 1, 1900 to June 6, 2079

SQL Server Date and time functions