Truncate Datetime to Second (Remove Milliseconds) in T-SQL

Question

What is the best way to shorten a datetime that includes milliseconds to only have the second?

For example 2012-01-25 17:24:05.784 to 2012-01-25

Answer 1

This will truncate the milliseconds.

declare @X datetime
set @X = '2012-01-25 17:24:05.784'
select convert(datetime, convert(char(19), @X, 126))

or

select dateadd(millisecond, -datepart(millisecond, @X), @X)

CAST and CONVERT
DATEADD
DATEPART