How to convert datetime to date only (with time se

问题:

I have a string '2009-06-24 09:52:43.000', which I need to insert to a DateTime column of a table.

But I don't care about the time, just want to insert it as 2009-06-24 00:00:00.000

How can I do that in T-SQL?

回答1:

For SQL Server 2005 and below:

CONVERT(varchar(8), @ParamDate, 112)    -- Supported way

CAST(FLOOR(CAST(@ParamDate AS float)) AS DATETIME)   -- Unsupported way

For SQL Server 2008 and above:

CAST(@ParamDate AS DATE)

回答2:

declare @originalDate datetime
select @originalDate = '2009-06-24 09:52:43.000'

declare @withoutTime datetime
select @withoutTime = dateadd(d, datediff(d, 0, @originalDate), 0)

select @withoutTime

回答3:

SELECT CAST(CONVERT(VARCHAR,GETDATE(),102) AS DATETIME)

SELECT CAST(CONVERT(VARCHAR(10),'2009-06-24 09:52:43.000',102) AS DATETIME)

回答4:

James is correct. If you're starting off with a string, and the format will always be what you say it is, then you keep it simple and efficient. Use LEFT( @StrDate, 10) and CONVERT that to your datetime value. Done.

If your input string could be any valid date/time format, then you have to use CONVERT(datetime, @StrDate) first. After that you go with what Bing just said to strip off the time part.

回答5:

An enhancement to the unsupported version: I am not sure if this may effect any performance. getdate() is an input timestamp in my query.

select cast(cast(getdate() as DATE) as DATETIME)

回答6:

I have found that casting as a date, then to a datetime to be very efficient and intuitive.

 SELECT CAST(CAST(GETDATE() as date) as datetime)

回答7:

If you will always have the date in the same format, i.e. yyyy-MM-DD you can grab the first 10 characters if the value and insert that which is the equivelant of 00:00:00.0000 time for that date.

select left('2009-12-32 4:32:00',10)

This is a very efficient way to do this as it does't require converting data types HOWEVER, it does require that the date will always be formatted with a four digit year and two digit day & month.

回答8:

cast it to a date, and then you can use CONVERT to get just the date.

INSERT MyTable(Column1)
SELECT CONVERT(CHAR(8), CAST('2009-06-24 09:52:43.000' AS DATETIME), 112)

回答9:

Probably a cleaner and more portable way to do this, but my years old idiom is:

insert into tbl (date_column)
select convert(varchar, convert (datetime, '2009-06-24 09:52:43.000'), 101)

回答10:

A variety of hacks:

• Convert your string to a datetime, then back again using the optional "style" parameter to convert to convert your datetime to a string using just the date portion
• use substring to chop off the end
• round the datetime using floor

回答11:

Strip the time, and cast it to date:

select cast(left(yourstring, 10) as datetime)