How to determine closest date

Question

I am a little confused about how or what the best way to determine what the closest date is to DateTime.Now is.

In my table, everything needs to be timestamped. And on a page, I need to be able to retrieve everything from the table only if the date is the closest date to now.

How would I go about this?

I am using DateTime.Now when inserting dates into the Database, and the format is like:

5/07/2011 5:28:57 PM

Answer 1

Here's my suggestion:

declare @DateTimeNow datetime = getdate()

select TOP (1)
     RecordId
    ,MyDateColumn
    ,abs(datediff(s, MyDateColumn, @DateTimeNow)) as Diff
from 
    MyTable
order by 
    abs(datediff(s, MyDateColumn, @DateTimeNow)) asc

Do not forget to use ABS()!

Answer 2

Do you only have past dates, meaning, will you ever have a date that is newer than DateTime.Now ? If not, you could get by with a simple Order By on the date column selecting the newest date. Otherwise, you'll need to get a date difference between your DateTime.Now , and order by that result. eg

SELECT TOP 1
   columnDate
FROM table1
ORDER BY DATEDIFF (ss,@passedInDate,columnDate)

This would essentially look for all future and past dates using your @passedInDate (DateTime.Now) as the qualifier or base date. I'm using seconds as the time interval to compare in my example, but you can change that to whatever makes the most sense for you.

Also, you shouldn't need to pass in DateTime.Now to SQL server, as you can use the built in GetDate() function.

Answer 3

How about

SELECT TOP 1 *
FROM MyTable
ORDER BY TimestampColumn DESC

Consider storing time in UTC - DateTime.UtcNow

Answer 4

In T-SQL you could use DateDiff:

DATEDIFF ( datepart , startdate , enddate )

http://msdn.microsoft.com/en-us/library/ms189794.aspx

or in C# you could use TimeSpan:

http://msdn.microsoft.com/en-us/library/system.timespan.aspx#Y3719

Answer 5

Something like this should work:

SELECT TOP 1 * FROM MyTable ORDER BY ABS(DATEDIFF(DD, getdate(), DATE))

This should sort your rows by the closest date, past or future. If you need it more precise then just days, change DD to something else, as specified here