sql server Date time 类型操作

Formatting Dates

Examples of calculating and formatting dates

*/

--To get the full Weekday name

SELECT DATENAME(dw,GETDATE())

--To get the abbreviated Weekday name (MON, TUE, WED etc)

SELECT LEFT(DATENAME(dw,GETDATE()),3)

--ISO-8601 Weekday number

SELECT DATEPART(dw,GETDATE())+(((@@Datefirst+3)%7)-4)

--Day of the month with leading zeros

SELECT RIGHT('00' + CAST(DAY(GETDATE()) AS VARCHAR),2)

--Day of the month without leading space

SELECT CAST(DAY(GETDATE()) AS VARCHAR)

--day of the year

SELECT DATEPART(dy,GETDATE())

--number of the week in the year

SELECT DATEPART(week,GETDATE())

--ISO-8601 number of the week of the year (monday as the first day of the week)

SET datefirst 1 SELECT DATEPART(week,GETDATE())

--you may need to preserve and restore the value

--full name of the month

SELECT DATENAME(MONTH,GETDATE())

--Abbreviated name of the month

SELECT LEFT(DATENAME(MONTH,GETDATE()),3)--not true of finnish or french!

--Number of the month with leading zeros

SELECT RIGHT('00' + CAST(MONTH(GETDATE()) AS VARCHAR),2)

--two-digit year

SELECT RIGHT(CAST(YEAR(GETDATE()) AS VARCHAR),2)

--four-digit year

SELECT CAST(YEAR(GETDATE()) AS VARCHAR)

--hour (00-23)

SELECT DATEPART(hour,GETDATE())

--Hour (01-12)

SELECT LEFT(RIGHT(CONVERT(CHAR(19),GETDATE(),100),7),2)

--minute

SELECT DATEPART(minute,GETDATE())

--second

SELECT DATEPART(second,GETDATE())

--PM/AM indicator

SELECT RIGHT(CONVERT(CHAR(19),GETDATE(),100),2)

--time in 24 hour notation

SELECT CONVERT(VARCHAR(8),GETDATE(),8)

--Time in 12 hour notation

SELECT RIGHT(CONVERT(CHAR(19),GETDATE(),100),7)

--timezone (or daylight-saving)

SELECT DATEDIFF(hour, GETDATE(), GETUTCDATE())

----ordinal suffix for the date

SELECT SUBSTRING('stndrdthththththththththththththththththstndrdthththththththst'

,(DATEPART(DAY,GETDATE())*2)-1,2)

--full date (the variations are infinite. Here is one example

SELECT DATENAME(dw,GETDATE())+', '+ STUFF(CONVERT(CHAR(11),GETDATE(),106),3,0,

SUBSTRING('stndrdthththththththththththththththththstndrdthththththththst'

,(DATEPART(DAY,GETDATE())*2)-1,2))

--e.g. Thursday, 12th Oct 2006/*

 

Calculating Dates by example

*/

-- now

SELECT GETDATE()

-- Start of today (first thing)

SELECT CAST(CONVERT(CHAR(11),GETDATE(),113) AS datetime)

--or ...

select DATEADD(dd, DATEDIFF(dd,0,getdate()), 0)

--or ...

SELECT cast(cast (GETDATE() as date) as datetime)

-- Start of tomorrow (first thing)

SELECT CAST(CONVERT(CHAR(11),DATEADD(DAY,1,GETDATE()),113) AS datetime)

-- Start of yesterday (first thing)

SELECT CAST(CONVERT(CHAR(11),DATEADD(DAY,-1,GETDATE()),113) AS datetime)

-- This time Next thursday (today if it is thursday)

SELECT DATEADD(DAY,((7-DATEPART(dw,GETDATE())+(((@@Datefirst+3)%7)+2)) % 7),GETDATE())

-- Two hours time

SELECT DATEADD(hour,2,GETDATE())

-- Two hours ago

SELECT DATEADD(hour,-2,GETDATE())

-- Same date and time last month

SELECT DATEADD(MONTH,-1,GETDATE())

-- Start of the month

SELECT CAST('01 '+ RIGHT(CONVERT(CHAR(11),GETDATE(),113),8) AS datetime)

-- Start of last month

SELECT CAST('01 '+ RIGHT(CONVERT(CHAR(11),DATEADD(MONTH,-1,GETDATE()),113),8) AS datetime)

-- Start of next month

SELECT CAST('01 '+ RIGHT(CONVERT(CHAR(11),DATEADD(MONTH,1,GETDATE()),113),8) AS datetime)

--last day this month

select dateadd(ms,-3,DATEADD(mm, DATEDIFF(m,0,getdate()  )+1, 0))

-- Ten minutes ago

SELECT DATEADD(minute,-10,GETDATE())

-- Midnight last night

SELECT CAST(CONVERT(CHAR(11),GETDATE(),113) AS datetime)

-- Midnight tonight

SELECT CAST(CONVERT(CHAR(11),DATEADD(DAY,1,GETDATE()),113) AS datetime)

-- Three weeks ago

SELECT DATEADD(week,-3,GETDATE())

-- Start of the week (this depends on your @@DateFirst setting)

SELECT DATEADD(DAY, -(DATEPART(dw,GETDATE())-1),GETDATE())

--first day of the current quarter

select DATEADD(qq, DATEDIFF(qq,0,getdate()), 0)

-- last year

SELECT DATEADD(YEAR,-1,GETDATE())

--final day of previous year

select dateadd(ms,-3,DATEADD(yy, DATEDIFF(yy,0,getdate()  ), 0))

-- new year, this year

SELECT CAST('01 Jan'+ DATENAME(YEAR,GETDATE()) AS datetime)

--or

select DATEADD(yy, DATEDIFF(yy,0,getdate()), 0)

-- new year, last year

SELECT CAST('01 Jan'+ DATENAME(YEAR,DATEADD(YEAR,-1,GETDATE())) AS datetime)

-- Last moment of this year

select dateadd(ms,-1,DATEADD(yy, DATEDIFF(yy,0,getdate()  )+1, 0))

-- next christmas

SELECT CASE WHEN DATEPART(dy,GETDATE())<DATEPART(dy,'25 Dec'+ + DATENAME(YEAR,GETDATE()))

THEN CAST('25 Dec'+ + DATENAME(YEAR,GETDATE()) AS datetime)

ELSE CAST('25 Dec'+ CAST(DATEPART(YEAR,GETDATE())+1 AS VARCHAR) AS datetime) END

 /*

 

Date Conversions

When converting from SQL Server dates to Unix timestamps, the dates are rounded to the nearest second (Unix timestamps are only accurate to the nearest second) SQL Server date to UNIX timestamp (based on seconds since standard epoch of 1/1/1970)

*/

 

SELECT DATEDIFF(second,'1/1/1970',GETDATE()) -- UNIX timestamp to SQL Server

SELECT DATEADD(second, 1160986544, '1/1/1970')

 

/* The newer datatypes can give some fascinating information. Here is an instant way of finding what the current time and date is, in a variety of parts of the world.*/

 

DECLARE @Timezones TABLE( timezone CHAR(6), Place VARCHAR(30))

INSERT INTO @Timezones (timezone, Place)

 VALUES

   ('-10:00', 'Hawaii'),

   ('-09:00', 'Alaska'),

   ('-08:00', 'Los Angeles'),

   ('-07:00', 'Arizona'),

   ('-06:00', 'Chicago'),

   ('-05:00', 'New York'),

   ('-03:00', 'Rio De Janeiro'),

   ('-01:00', 'Azores'),

   ('-00:00', 'London'),

   ('+01:00', 'Berlin'),

   ('+02:00', 'Cairo'),

   ('+03:00', 'Moscow'),

   ('+04:00', 'Dubai'),

   ('+05:00', 'Islamabad'),

   ('+05:30', 'Bombay'),

   ('+07:00', 'Bangkok'),

   ('+08:00', 'Beijing'),

   ('+09:00', 'Tokyo'),

   ('+10:00', 'Sydney'),

   ('+12:00', 'Auckland')

SELECT

  Place, CONVERT(CHAR(20), SWITCHOFFSET(SYSDATETIMEOFFSET( ), timezone), 113)

FROM @timezones ORDER BY  place

/* We've put a fuller version of this in the speechbubble at the top of the article.

Using dates

When storing dates, always use one of the date/time data types. Do not feel tempted to use tricks such as storing the year, month or day as integers, with the idea that this

will help retrieval and aggregation for reports. It never does.

if you use the DATETIMEOFFSET, you are reasonably future-proof as you store dates as the UTC date together with the offset. This means that you can do dime-and-date calculations on data, even if it has been taken from more than one time zone.

The manipulation of the date/time data types is so critical to SQL Server's performance that it is highly optimised. indexes based on date/time data type work very well, sort properly, and allow fast partitioning on a variety of criteria such as week, month, year-to-date and so on.

If, for example, you store a list of purchases by date in a table such as PURCHASES

you can find the sum for the previous week by... */

 

SELECT SUM(total) FROM purchases

WHERE purchaseDate BETWEEN DATEADD(week,-1,GETDATE()) AND GETDATE()

--this will pick up an index on PurchaseDate

--what about sales since the start of the week

 

SELECT SUM(total) FROM purchases

WHERE purchaseDate BETWEEN

DATEADD(DAY, -(DATEPART(dw,GETDATE())-1),GETDATE()) AND GETDATE() --Want a daily total?

SELECT CONVERT(CHAR(11),PurchaseDate,113),

SUM(total) FROM purchases

GROUP BY CONVERT(CHAR(11),PurchaseDate,113)

ORDER BY MIN(PurchaseDate)

 

--Or to find out which days of the week were the best?

SELECT DATENAME(dw,PurchaseDate),

[No. Purchases]=COUNT(*), [revenue]=SUM(total) FROM [purchases]

GROUP BY DATENAME(dw,PurchaseDate), DATEPART(dw,PurchaseDate)

ORDER BY DATEPART(dw,PurchaseDate)

--Want a week by week total?

SELECT 'Week '+DATENAME(week,purchaseDate)+' '+DATENAME(YEAR,purchaseDate),

SUM(total) FROM purchases

GROUP BY 'Week '+DATENAME(week,purchaseDate)+' '+DATENAME(YEAR,purchaseDate)

ORDER BY MIN(InsertionDate)

 

--(you'd miss weeks where nothing was purchased if you did it this way.)

/* The LIKE expression can be used for searching for datetime values.

If, for example, one wants to search for all purchases done at 9:40, one can find

a match by the clause WHERE purchaseDate LIKE '%9:40%'. */

SELECT * FROM [purchases]

WHERE purchaseDate LIKE '%9:40%'

 

--or all purchases in the month of february

SELECT COUNT(*) FROM [purchases]

WHERE purchaseDate LIKE '%feb%'

 

--all purchases where there is a 'Y' in the month (matches only May!)

SELECT DATENAME(MONTH, insertionDate), COUNT(*) FROM [purchases]

WHERE purchaseDate LIKE '%y%'

GROUP BY DATENAME(MONTH, purchaseDate)

/* this 'Like' trick is of limited use and should be used with considerable caution as

it uses artifice to get its results*/